Unmanned aerial vehicle take-off and landing systems

ABSTRACT

Unmanned aerial vehicle take-off and landing systems are disclosed herein. In one embodiment, a method of landing an unmanned aerial vehicle includes programming a landing location for the unmanned aerial vehicle utilizing a user input device. The unmanned aerial vehicle is launched. Communications between the unmanned aerial vehicle and the user input device are interrupted, and the unmanned aerial vehicle is landed at the landing location based on the programmed landing location and not based on any real-time communication between the unmanned aerial vehicle and the user input device.

REFERENCE TO RELATED CASES

The present application is a continuation of and claims priority of U.S.patent application Ser. No. 12/712,581, filed Feb. 25, 2010, which isbased on and claims the benefit of U.S. patent application Ser. No.12/008,176, filed Jan. 9, 2008, now U.S. Pat. No. 7,693,624, issued Apr.6, 2010, which is based on and claims the benefit of U.S. patentapplication Ser. No. 10/871,612, filed Jun. 18, 2004, now U.S. Pat. No.7,343,232, issued Mar. 11, 2008, which is based on and claims thebenefit of U.S. provisional patent application Ser. No. 60/480,192,filed Jun. 20, 2003, the content of all of these documents being herebyincorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a system utilized to control a vehicle.More particularly, the present invention pertains to a variable autonomycontrol system that enables a human to manage and operate a vehiclethrough interaction with a human-system interface.

Vehicle control systems are well known in the art, one known examplebeing a control system that enables a human operator to remotely manageand control an unmanned vehicle. In one known application, an operatorremotely controls an unmanned aerial vehicle (UAV) through ahuman-system interface. The operator typically controls details relatedto payload, mission and/or flight characteristics of the unmannedaircraft.

The development of practical applications for UAV technology has beenhindered by an absence of a well-integrated control and guidance system.Potential applications for UAV's include border patrol, trafficmonitoring, hazardous area investigation, atmospheric sampling or evenmotion picture filming. All of these and other UAV applications wouldbenefit from a control system that enables a person with minimalaviation experience or manual skill to operate the vehicle. Withpresently known systems, the operator is rarely able to focus on payloador mission operation because he or she is consumed with the significantresponsibilities associated with aircraft piloting.

In order to be truly versatile, UAV control systems should becomfortably usable by individuals with training that is focused on therequirements of a given mission or on the usability of a payload, ratherthan on the aviation of the air vehicle. In many cases, present systemsrequire an individual with pilot training to engage a control system andmanage mission, payload, and aviation functions simultaneously. It isnot common for known control systems to be configured for the support ofintuitive high level commands such as “go left”, “go right”, “take off”,“land”, “climb”, or “dive”. It is instead more typical that knowncontrol systems require low-level stick-and-rudder commands from theoperator. Thus, there is a need for a control system that supportsintegration of intuitive, mission-level remote commands into a UAVguidance system, thereby significantly reducing the work load on a humanoperator as it pertains to vehicle aviation.

Known control systems are generally not configured to support multiplelevels of autonomous operation. In fact, few systems even offerautonomous or semi-autonomous mission capability packaged with anability to remotely interrupt the mission. Thus, for known systems, theworkload of the operator is generally too great to enable him or her tofly multiple UAV's from a single ground control station, which is anappealing possibility. Thus, there is a need for a flexible vehiclecontrol and management concept that will operate even when responding toremote intuitive commands such that one person can operate multiplevehicles from the same control station.

Known UAV control systems typically offer limited real-time controlcapability or they require management by rated pilots. It is known forsystems to have a capability to automatically follow pre-planned missionroutes. However, it is common that real-world missions fail to goexactly as planned. For example, time-critical targets or surveillanceobjectives can pop up during the mission; traffic conflicts with mannedaircraft can occur; clouds can get in the way of sensors (e.g., EO/IRsensors); or intelligent and devious adversaries can make targetlocation and identification difficult. Real-time control is required todeviate from the planned route to find and identify new targets; tomaneuver UAV's to avoid traffic; to fly under the weather; or to getbetter line-of-sight-angles. Skilled pilots can maneuver aircraft, butthen an additional operator is typically necessary to manage sensorsand/or the dynamic mission.

While commercialized products such as video games and CAD utilities nowprovide an excellent model for human interfaces, such interfaces havegenerally not been completely integrated into an actual vehicle controlsystem. In fact, very few known UAV autopilot systems are readilycompatible with known Commercial Off-The-Shelf (COTS) hardware. This isunfortunate because it is not uncommon for non-pilot trained individualsto be pre-equipped with a familiarity with such hardware that includesstandard joysticks, track-balls, lap-top computers, virtual reality headmounted displays and glove input devices.

Known vehicle control systems generally do not include an operationalmode that enables an operator to focus his or her attention on atactical situation display (e.g., images transmitted from an onboardsensor) rather than providing directional commands based primarily on acontrol interface. Such a control mode has many potential advantageousapplications, for example, an operator can command the scope of thevehicle's on-board sensor to survey a battle field (or othertopographical region) while the vehicle autonomously commands a flightprofile that is slaved to the operator's sensor line-of-sight commands.There is a need for an integrated guidance solution that adapts to sucha mode of control.

Advances in virtual reality simulation graphic display technology havemade the concept of a virtual reality interface to real-time systemsfeasible. Already used by surgeons in the medical community, the use ofvirtual reality, such as Telepresence or Mixed Reality systems, in thecontext of UAV control is now feasible but generally unknown. Thus,there is a need for a control system that provides an operator withfunctionality that takes advantage of this new technology.

Finally, many known control systems are not adaptable to on-goingcommand-and-control software development efforts. For example, formilitary applications, it is desirable that a control system be equippedto operate within the advanced Command Control Communication Computersand Intelligence (C4I) infrastructure and interface with associatedCommon Ground Control Stations such as the Joint STARS Common GroundStation. It is desirable that guidance software have the capability notonly to respond to the command interface, but also an ability to beexpanded modularly as new capabilities are desired, such that expansionscan be accomplished without significant changes in the interface.

SUMMARY OF THE INVENTION

Embodiments of unmanned aerial vehicle take-off and landing systems aredisclosed herein. In one embodiment, a method of landing an unmannedaerial vehicle includes programming a landing location for the unmannedaerial vehicle utilizing a user input device. The unmanned aerialvehicle is launched. Communications between the unmanned aerial vehicleand the user input device are interrupted, and the unmanned aerialvehicle is landed at the landing location based on the programmedlanding location and not based on any real-time communication betweenthe unmanned aerial vehicle and the user input device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram illustrating a variable autonomycontrol system.

FIG. 2 is a schematic representation of a human-based command andcontrol loop.

FIG. 3 is a diagrammatic block representation of a hierarchical controlstructure.

FIG. 4 is a simplified diagrammatic representation of a controlstructure.

FIG. 5 is a diagrammatic block representation of a control systemincorporating a translation layer.

FIG. 6 is a schematic representation of top-level software objectsassociated with system interface components of a control system.

FIG. 7 is a schematic representation of an interface system for thecontrol of multiple vehicles.

FIG. 8 is a schematic diagram representing a vehicle control scheme.

FIG. 9 is a control diagram representing a general integrated guidanceloop structure.

FIG. 10-1 is a diagrammatic representation of an ECEF coordinate framedefinition.

FIGS. 10-2 and 10-3 are diagrammatic representations of a geodeticcoordinate frame definition.

FIG. 10-4 is a schematic representation of a body reference frame.

FIG. 11 is a schematic block diagram demonstrating a basic flowstructure for various flight mode levels.

FIG. 12 is a schematic diagram demonstrating waypoint guidance errorcalculation.

FIG. 13 is a schematic diagram demonstrating the effect that the earth'scurvature can have on calculations.

FIG. 14 is a schematic diagram demonstrating altitude error calculation.

FIG. 15 is a schematic diagram demonstrating one aspect of waypoint legtransition.

FIG. 16 is a schematic diagram demonstrating a vehicle turn.

FIG. 17 is a schematic diagram defining parameters and coordinate framesused to support an elliptical loiter guidance law.

FIG. 18 is a schematic chart demonstrating that for any point P outsideof an ellipse there exist two lines passing tangent to the ellipse andcontaining the point P.

FIG. 19 is a schematic diagram demonstrating segments associated withracetrack and figure-8 patterns.

FIG. 20 is a schematic diagram demonstrating an example of a programmedroute using various loiter algorithms.

FIGS. 21, 22A & 22B are schematic diagrams demonstrating features of aline-of-sight-slave control approach.

FIG. 23 is a schematic illustration of a scan process in the context ofa ground collision avoidance system.

FIG. 24 is a schematic diagram illustrating a fly-out trajectory in thecontext of a ground collision avoidance system.

FIG. 25 is a simplified block diagram of a ground control station.

FIG. 26 is a block diagram representation of an example graphical userinterface display.

FIG. 27 is a sample screen shot representation of a vehicle statusdisplay.

FIG. 28 is an example screen shot representation of an intelligentwindow display.

FIGS. 29-33 are examples of pop-up window displays.

FIG. 34 is a schematic diagram demonstrating a generic vehicle classsystem configuration.

FIGS. 35 & 36 are examples of vehicle-specific window displays.

FIG. 37 is an example screen shot representation of a graphical userinterface.

FIG. 38 is a schematic block diagram demonstrating a network centric UDPcommunications scheme.

FIG. 39 is a schematic block diagram illustrating potential controlpaths through a mission.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

I. Introductory Comments

Much of the present invention description will be devoted to describingembodiments in the context of an unmanned aerial vehicle (UAV). However,it is to be understood that the embodiments generally pertain to vehiclecontrol systems and are designed for broad application. The embodimentscan be adapted by one skilled in the art to be applied in the context ofany of a variety of unmanned vehicles including, but not limited to,airplanes, helicopters, micro air vehicles (MAV's), missiles,submarines, balloons or dirigibles, wheeled road vehicles, trackedground vehicles (i.e., tanks), and the like. Also, embodiments of thepresent invention can be adapted by one skilled in the art to beimplemented in the context of manned vehicles (e.g., a human passengeroperates the control system, or a human remotely operates a controlsystem for a vehicle that transports a passenger, etc). It should benoted that the relatively modular nature of the vehicle control systemof the present invention enables the adaptations necessary toaccommodate different vehicles to be made in a relatively small periodof time.

Certain embodiments of the present invention pertain to specializedcontrol subsystems that each individually enable a specific controlfunctionality to be accessed through the larger control system. It is tobe understood that such subsystems can be adapted and independentlydeployed even in the context of vehicle control systems other than thosespecifically described herein. Also, such subsystems can be adapted tosupport any type of manned or unmanned vehicle including, but notlimited to, those specifically listed herein.

II. Overview—Variable Autonomy Control System

Architecture

Embodiments of the present invention generally pertain to a variableautonomy control system (VACS) architecture that enables, among othercharacteristics, a general simplification of UAV operation and control.The architecture illustratively supports selectable levels of controlautonomy from fully autonomous control to simplified manual flightcontrol modes for enhanced real-time control.

As dependence on UAV's for military operations grows and UAV technologyis integrated into the emerging global command and control architecture,the cost and complexity of managing and controlling these assets couldeasily become substantial. This limitation is brought about by either oftwo extremes in the vehicle command and flight control philosophy:complete dependence on a human-in-the-loop (fully manual control) orcomplete exclusion of a human-in-the-loop (fully autonomous control).The former requires a dedicated, highly trained operator whereas thelatter provides no mechanism for real-time operator interaction ormission management. The need for a dedicated highly-trained operatordrives costs (personnel and training requirements) and severely limits asingle operator's flexibility in that he or she is primarily focused onthe aviation of the vehicle rather than the higher level missionobjectives. On the other hand, the exclusion of the human-in-the-loopdrives logistics costs (mission planning and asset allocation) andseverely limits the UAV's operational flexibility.

A control design consistent with embodiments of the present inventionexploits existing flight control technologies to arrive at an idealbalance between the two above-described control philosophies. Thecontrol design includes a flight control structure that supportsvariable levels of control autonomy and minimizes personnel and trainingrequirements for vehicle operation. Human factors play a key role inthat the vehicle is treated as one of many assets (e.g., including othervehicles) available to an individual operator during the execution of adefined mission. Therefore, the vehicle must be easily controllable.Embodiments of the present invention reflect the philosophical notionthat a truly enabled UAV operator should not be required to be a trainedaviator but should still retain variable levels of control capability toexecute mission objectives that call upon his/her specialized expertise.

Embodiments of the present invention pertain to a hierarchical flightcontrol structure with varied levels of remote operator input combinedwith an off-board controller software package and intuitive human systeminterface. Research of problems related to UAV control has indicatedthat a good solution lies in the appropriate functional allocationbetween human and machine. In the context of embodiments of the presentinvention, this leads to segregation of control into two fundamentalcategories: flight control and flight management. Flight controlassociates with the aviation of the aircraft whereas flight managementassociates with the mission plan (navigation tasking) for the aircraft.

III. Details—VACS Architecture

FIG. 1 is a schematic block diagram illustrating a VACS architecture 100in accordance with one aspect of the present invention. Architecture 100incorporates a hierarchical design that enables an invocation ofdifferent control behaviors at various levels in the hierarchy.Primitive control functions are combined with complex autonomousfunctions to enable a broad range of behaviors. An operator isillustratively able to access and selectively invoke certain of thecontrol behaviors through an intuitive interface, such as an interfacemade available through a workstation. In accordance with one embodiment,the architecture design enables a single operator to work through theinterface to effectively control multiple vehicles simultaneously.

FIG. 1 includes a spectrum 102 that demonstrates the hierarchical natureof architecture 100. Inputs 106 from human and other external sourcesare characterized across spectrum 102. At the top of the spectrum is theobjective/decision level 104. Level 104 represents the highest end ofthe control spectrum wherein autonomous control is maximized, and thelevel of intelligent interaction (e.g., interaction with a human orother systems) consists of higher-level objective-based planning. Thelowest level of intelligent autonomy is the execution level 112, inwhich external command interaction is either directly proportional tothe actuation or is minimally compensated.

In between ends 104 and 112 are mission level 108 and coordination level110. Levels 108 and 110 are sub-levels of the spectrum and representvarying levels of a blending of external and automated functionality.Mission level 108 is more human-oriented than coordination level 110,which is more human-oriented than execution level 112. Conversely,execution level 112 is more autonomous in nature than coordination level110, which is more autonomous in nature than mission level 108.

Architecture 100 includes a plurality of functional sub-components120-146. With regard to the FIG. 1 depiction, it should be noted thatthe individual functional sub-components are not necessarily illustratedon the level where they would correspond to the illustrated spectrum102. Spectrum 102 is provided simply to demonstrate a hierarchicalstructure underlying architecture 100. Functional sub-components 120-146represent control behaviors available for invocation eitherautomatically or based on operator selection inputs.

When the illustrated control system architecture is actually applied,two or more of the illustrated functional sub-components can be appliedsimultaneously to accomplish a unified control scheme. In addition, inaccordance with one embodiment, an operator is provided with thecapability to interact through an interface to activate and deactivatecertain functional control sub-components in order to activate anddeactivate different modes of operator control representing differentlevels of system autonomy. An intelligence synthesizer 150 is providedto coordinate applicable functional sub-components and resolve conflictsthere between. For example, if a vehicle is autonomously tracking atarget (sub-component 130) and a new control command is inserted toautomatically avoid an air collision (sub-component 122), then it isillustratively up to intelligence synthesizer 150 to determine whichcontrol source is to be given priority. Assumedly, collision avoidancewill be given priority. Following execution of collision avoidance,intelligence synthesizer 150 is illustratively configured to resumenormal operation (e.g., resume target tracking, hold a reasonableheading, etc.). In another example, if an operator interrupts thetracking of a target with an instruction to switch to autonomous routefollowing (sub-component 132), then intelligence synthesizer 150 willensure that the switch between modes of control is carried out assmoothly and efficiently as possible.

In accordance with one embodiment, intelligence synthesizer 150 isconfigured to manage the interfaces between modular autonomous andsemi-autonomous functions so that they can be integrated in a‘plug-n-play’ format. Some functions require de-confliction betweencompeting commands to the airframe, on-board sensors, or outer-loopguidance. The intelligence synthesizer is illustratively configured todetermine what functions exist in the configuration, what functions havepriority, what functions are dormant, and what functions do not exist inthe configuration. The intelligence synthesizer is illustrativelyfurther configured to implement the VACS hierarchical architecture tomanage which level autonomy is allocated to each function. Withreference to the FIG. 1 architecture hierarchy, the lowest levelExecution functions are implemented with direct interfaces to theairframe and payload hardware. These functions illustratively include anairframe body-rate stabilization loop, an airframe accelerationcommand-tracking loop, a bank-angle command tracking loop, and/or acollection of payload management functions (these and other applicablefunctions are commercially available for integration and/or aredescribed in other sections below as embodiments of the presentinvention). The higher level functions have interfaces as well, and insome cases will illustratively share responsibility with CoordinationLevel functions. Examples of such functions include implementation ofinertial trajectories, pre-programmed maneuvers such as racetrack loiterpatterns, waypoint leg regulation and switching, management of awaypoint list, and management of semi-autonomous control functionalitysuch as sensor slave and remote-directional control (these and otherapplicable functions are commercially available modules for integrationand/or are described in detail below in other sections as embodiments ofthe present invention).

The Coordination level functions illustratively share responsibilitieswith some Mission level functions. Examples of mission-level functionsare autonomous route planners, autonomous ground collision avoidance,and autonomous see-and-avoid (these and other applicable functions arecommercially available modules for integration and/or are described indetail below in other sections as embodiments of the present invention).Generally speaking, these functions process mission-level requirementsand implement them based on vehicle state and mission statusinformation.

In accordance with one embodiment, autonomous and semi-autonomousfunctions illustratively communicate and coordinate with each other viaintelligence synthesizer 150, which is a pseudo-bus and communicationsmanager. In cases where autonomous commands conflict or interfere witheach other, intelligence synthesizer 150 determines how to de-conflict,blend, or prioritize the output commands.

A payload control functional sub-component 144 is included in order tofacilitate transfers of information to and from mission payload 160.Mission payload 160 is illustrated with a variety of payload components162-176. The illustrated payload components are illustrative only inthat other or different components could be included without departingfrom the scope of the present invention. Some of the payload componentsare sensors that gather data that is transferred to intelligencesynthesizer 150 either for the purpose of serving as a reference to beutilized in a vehicle control scheme or, alternatively, to be collectedfor some inherent value of the information itself (e.g., collected for amission-oriented purpose). One illustrative purpose for communicationpayload component 174 is to facilitate communication between a groundstation and a corresponding system implemented on the remote vehicle.Embodiments of the present invention pertain to specific communicationscomponents and will be described in greater detail below in othersections. Weapons payload component 176 is an example of an activecomponent that can be triggered (e.g., fired) in response to operatorinput. Many of the illustrated payload components will be described ingreater detail below. Chemical-biological detector component 172 isillustratively a sensor for detecting chemical and/or biologicalsubstances, for example for the purpose of identifying areascontaminated by chemical or biological agents. The GPS/IMU component 170is illustratively a vehicle motion identification component forgenerating vehicle location information for any purpose such as, but notlimited to, vehicle guidance, navigation or to be viewed by the operator(these and other applications of the data provided by sensor 170 will bedescribed below in greater detail). Camera component 164 gathersinformation for mission purposes and/or for control purposes (the latterpurpose being an embodiment of the present invention that will bedescribed in detail below in other sections). Optical tracker 162 isillustratively configured to track an airborne or ground-based objectrelative to the vehicle for control purposes (e.g., air collisionavoidance, ground target tracking, air target tracking, etc.) or missionpurposes. Components 166 and 168 support additional mission and/orcontrol functionality. Component 166 facilitates data collection andtransfer of information in the nature of radar data, SAR data, ISAR dataor the like. Component 168 could be any of a variety of components butillustratively facilitates data collection and transfer of informationin the nature of a radar emitting device configured to sense and locateground objects and the like.

The VACS architecture 100 illustratively enables a man-in-the-loop(i.e., the operator) to intuitively assign and deploy one or more UAV'sin accordance with available control behavior parameters. Thearchitecture supports intuitive control characteristics that areillustratively based on the human learning and decision-making process.Accordingly, the available control behavior parameters are designed toemulate the human learning, decision-making, and action processes. Thearchitecture is distributed by design so that appropriate learning,decision-making and action behaviors are resident onboard the vehicleand supported with autonomous functionality when necessary.

It should be emphasized that the present invention is not limited to theillustrated sub-components 120-146. In fact, in accordance with oneembodiment of the present invention, architecture 100 is designed suchthat additional sub-components can be modularly plugged into controlarchitecture 100 to extend the system functionality. When a newsub-component is installed, intelligence synthesizer 150 isillustratively configured to recognize and manage the new functionality(e.g., synthesizer 150 is configured to manage conflicts with othersub-components, etc.).

FIG. 2 is a schematic representation of a human-based command andcontrol loop 200 as is emulated in the VACS architecture 100. Forreference purposes, FIG. 2 includes the same intelligent controllerhierarchy spectrum 102 that was illustrated in FIG. 1. At the highestend of the spectrum, objectives 202 (e.g., typically human defined suchas reconnaissance, surveillance, tracking, monitoring, etc.) provide afundamental basis for the subsequent support levels. The lower levels ofactivity will illustratively be influenced by the overarchingobjectives. For the machine or vehicle, the fundamental equivalent ofobjectives 202 is machine constraints 204 (e.g., aviation limitations ofthe vehicle, available payload components, communications limitationssuch as range, static and dynamic limitations, etc.). The overarchingmachine constraints illustratively influence the lower levels ofactivity. In accordance with one aspect of the present invention, ahuman (i.e., an operator) can utilize a machine (e.g., a UAV) that isequipped with a system implementing the VACS architecture to observe(bubble 206), orient (bubble 208), decide (bubble 210) and take action(bubble 212). The steps of observe, orient, decision and action arehierarchical in nature and reflect a natural human process flow, andnotably are reflected in the available coordination of autonomousfunctionality offered through the VACS architecture.

FIG. 3, in accordance with one aspect of the present invention, is adiagrammatic block representation of a hierarchical control structure300. Control structure 300 is illustratively designed to support theVACS architecture 100 described in relation to FIG. 1. Most of thefunctional sub-components illustrated in FIG. 1 represent a range ofpotential functional control capabilities incorporating different levelsof autonomy. Again, as has been discussed, the architecture is designedto be modularly extendable to even non-illustrated control schemes.

The highest level of control structure 300 is level 302, which isidentified as the trajectory control level. Level 302 representsautonomous flight control modes and functionality that basicallyincorporate substantially full autonomy requiring practically nooperator input. For illustrative purposes, mission control 304 isincluded on level 302 and represents mission-oriented fully autonomousflight control (e.g., mission is automatically planned and executed).

The next level of control structure 300 is level 306, which isidentified as the inertial guidance level. Level 306 broadly representsautonomous flight control functionality with operator inserted pathcommands such as, but not limited to, waypoint editing, loiter pointediting or real-time route editing. For illustrative purposes,take-off/landing control 308 and path control 310 have been included onlevel 306 (it is assumed that both are autonomous to some extent butrequire operator path input). To simplify the diagram, only a fewrelevant modes and functions are noted in the Figure specifically.

As is demonstrated on level 306, some sub-components or functions can beconfigured to work in cooperation with others. For example, take-off andlanding components may utilize waypoint component functionality ingeneration of a flight approach for landing purposes. Such functionalinterdependence is within the scope of the present invention. Further,it should be noted that FIG. 3 is similar to FIG. 1 in that it is simplyintended to demonstrate a hierarchical organization scheme in accordancewith one aspect of the present invention. Actual characterization of thedifferent functional components is open to interpretation.

In accordance with one aspect of the present invention, box 312represents a specific level 306 autonomous mode of control that is worthpreviewing as an example. Box 312 represents a line-of-sight slavecontrol mode of operation wherein a payload sensor is integrated intothe guidance loop such that the vehicle is slaved to operator commandedsensor-pointing angles. In one embodiment of this control mode, theoperator is generally concerned primarily with pointing the sensor withhis/her attention focused on sensor imagery. The sensor commands arethen blended into the UAV guidance algorithms and airframe stabilizationcommands are computed to orient the vehicle optimally in the missionenvironment. This control mode illustratively provides the foundationfor a virtual reality human system interface, such as a head mounteddisplay, and facilitates telepresence (the linking of remote sensors inthe real world to the senses of a human operator) of surveillance andreconnaissance.

The next level of control structure 300 is level 316, which isidentified as the directional control level. Level 316 broadlyrepresents a hybrid level of autonomous flight control including, inaccordance with one aspect of the present invention, as is notablydepicted as an insert above block 318, remote directional command (RDC)capability. In accordance with one embodiment of RDC control, anoperator can select a preprogrammed vertical profile maneuver (such asmax climb or in-route descent) and maintain manual horizontaldirectional control of the vehicle. The operator can instantaneouslytransition to a control mode in which he/she has complete directionalcontrol (both vertical and horizontal) of the vehicle without beingrequired to stabilize it rotationally. In accordance with oneembodiment, the operator's control stick commands are mapped todirectional commands (horizontal turn rate and climb/descent rates) thatare then transformed into acceleration and bank angle commands prior tobeing fed into a stabilization autopilot, which is represented on level320.

In accordance with one embodiment of the present invention, as isrepresented by box 318, control commands, regardless of their functionalsub-component source, are transformed into acceleration and bank anglecommands. These commands are then passed to the next level of thecontrol structure, namely level 320, which is illustratively identifiedas the disturbance rejection autopilot level. In accordance with oneaspect of the present invention, all levels of control utilize the sameautopilot for a given vehicle, which in the illustrated case is abody-rate stabilization component 322.

The lowest level of control structure 300 is level 330, which isillustratively the level wherein actual manipulation of the aircraft'saerodynamic surfaces and thrust control occurs. Control commands afterbeing filtered through autopilot component 322 are executed on level330. In accordance with one embodiment, as is illustrated on level 330as an arrow insert, one mode of control involves direct control of theaviation surfaces. Accordingly, such control commands are effectuated ata level below level 320 and are therefore relatively manual in nature.

In accordance with one embodiment of the present invention, the controlmodes and functions above box 318 generally do not require the operatorto possess particularly specialized skills in aircraft aviation. On topof these control modes and functions, the UAV flight control computerperforms higher frequency inner loop stabilization and command tracking(e.g., boxes 318 and 322). To the extent that control conflicts arisewherein multiple sub-components or functions generate conflictingcontrol requests, intelligence synthesizer 150 is illustrativelyconfigured to resolve such conflicts prior to generation of accelerationand bank angle commands (box 318).

In accordance with one aspect of the present invention, the describedvehicle control scheme supports transitions between changing controlmodes and functions. For example, suppose a UAV is flying a set ofwaypoints and the operator edits the waypoints. A transition must bemade from the old waypoints to the new waypoints. In another example,suppose an aircraft flying a set of waypoints is on course to collidewith another aircraft. It is within the scope of the present inventionthat an air collision avoidance sub-component will override the waypointpath and direct the aircraft off of the collision course. In this case,in accordance with one embodiment, the commands generated for level 316will first correspond to the requested waypoint path, then there will bea transition to a non-collision path, and then there will be a gracefultransition back to the waypoint path.

In accordance with one aspect of the present invention, intelligencesynthesizer 150 is customized to support incorporated sub-components andfunctions and is thereby configured to generate the control commandsnecessary to transition control between sub-components and/or functionsas necessary (e.g., acceleration and bank angle commands are obtainedand executed as necessary for transitions). In accordance with anotherembodiment, information for resolving functional conflicts is embeddeddirectly into a sub-component or function itself. It is also within thescope of the present invention that transitions be handled from bothlocations (e.g., some transitions are processed by the intelligencesynthesizer and others are addressed directly within the sub-componentsor functions).

Generally speaking, FIG. 3 represents a top-level flow diagram of howthe Mission, Coordination and Execution-Level hierarchical controlarchitecture is organized so that external commands can be easilyinjected in to the autonomous control structure. The highest-levelcommands issued by the mission-level functions can be overridden orblended with trajectory edits inserted by a human operator, for example,via a ground control station interface. These commands are sent down tothe inertial path regulation control loops, which generate airframeacceleration commands (or flight-path equivalent). If the user injectsjoystick steering commands, they are translated to the equivalent bodyacceleration commands, which are gracefully blended into the commandchain by the VACS software. The acceleration commands are translated tobank angle and normal acceleration commands, which are articulated bythe acceleration tracking and rate stabilization loops. The VACSarchitecture also provides an insertion point for low-level commands(e.g., stick-and-rudder commands), which correspond to more traditionalinputs for piloted aircraft. These commands are directly input to theservos and override all of the other autonomous commands coming into thesystem.

FIG. 4 is a simplified diagrammatic representation of a controlstructure 400 in accordance with one aspect of the present invention.Control structure 400 includes a funnel representation 402 thatrepresents a funneling of sub-component control functions into anacceleration control and bank angle command generator 404. In accordancewith one embodiment, the information transferred to component 404incorporates as necessary resolutions for functional conflicts andtransitions between control modes or functions.

Information received by component 404 is transformed into correspondingacceleration and bank angle commands. These commands are thentransferred to autopilot component 406, which in accordance with oneembodiment, is configured to make control adjustments as necessary tomaintain vehicle stabilization and/or track control commands.Accordingly, all levels of control are filtered through the sameautopilot for a given vehicle. In accordance with one embodiment,autopilot component 406 is configured to make adjustments as necessaryto maintain stability across control modes. The autopilot functionalityis generally fixed and generally does not change regardless of modeselections or changes (e.g., all commands are funneled through the sameautopilot). A mode change does not require the autopilot to be reset.Accordingly, the present invention provides continuity at the autopilotlevel, which is excellent for mode transition. This is an advantage overknown systems wherein mode changes are known to cause instability, suchas systems that incorporate a different autopilot for different modes.

As will be discussed in greater detail below, the control system andarchitecture embodiments of the present invention essentially enable anyautopilot design to support control of a vehicle in numerous controlmodes that are executed with switches between modes during flight. Allcontrol modes are supported even in the presence of sensor errors, suchas accelerometer and gyro biases. This robustness is at least partiallyattributable to the fact that the closed-loop system, in all controlmodes, is essentially slaved to an inertial path and, hence, the sensorbiases wash out in the closed loop, assuming the biases are not sogrossly large that they induce stability problems in the autopilotsystem. Furthermore, winds are generally not an issue in the overallcontrol scheme in that the flight control system will regulate to theinertial path, adjusting for winds automatically in the closed loop.Given the precision afforded by inertial navigation aided by GPStechnology, inertial path regulation offers a highly effective androbust UAV control approach. Generally speaking, the autopilot systemfunctions such that winds, medium Dryden turbulence levels, sensorerrors, airframe aerodynamic and mass model parameter uncertainties,servo non-linearity (slew rate limits, etc.), and various otheratmospheric and noise disturbances will non have a critically negativeimpact on flight path regulation.

Component 408 receives commands generated by component 404 and filteredby autopilot component 406. The commands received by component 408 areexecuted to actually manipulate the vehicle's control surfaces.Autopilot component 406 then continues to monitor vehicle stabilizationand/or command tracking, making additional commands to component 408 asnecessary.

Generally speaking, relative to the control structures illustrated inFIGS. 3 and 4, known control systems are inflexible. For example, someknown systems support little or no control functionality beyond remotestick-and-rudder commands (e.g., direct control of vehicle controlsurfaces with little or no incorporated automation). To the extent thata known system offers multiple modes of vehicle control, the modes aretypically rigid in nature rather than flexible.

In accordance with one aspect of the present invention, an entirehierarchical spectrum of multi-autonomous control modes are madeavailable to a system operator. The operator is illustratively able toefficiently and smoothly change control modes mid-mission as desired.The operator can do much more than simply change, edit or adjustwaypoints on a waypoint-following mission. An operator can interrupt awaypoint-following mission to guide the vehicle manually, or partiallymanually (e.g., remote directional commands), or based on sensor/remoteline-of-sight command control. In accordance with one embodiment, thecontrol system is configured to optionally transition back to aninterrupted mission (e.g., back to an original waypoint-followingmission). It should be noted that the “operator” is not necessarilyhuman. For example, the operator could be an automated decision-makingsource, such as a military C4I system.

The spectrum of control modes available to an operator illustrativelycorresponds to the particular functional sub-components incorporatedinto the variable autonomy control system architecture (e.g.,architecture 100 in FIG. 1). In accordance with one aspect of thepresent invention, in addition to numerous specific control modes thatwill be described within the present description, a spectrum ofadditional control modes are conceivable. The control systems of thepresent invention can be easily configured to support (includingconflict and transition support that enables the operator to switch backand forth between modes) basically any control mode or module. Examplesof such control modes include:

1. Operator inputs a planned route and then the control systemautonomously chooses a vehicle (e.g., one of several available vehicles)and automatically guides the vehicle along the planned route . . . oroperator designates a moving ground target and then the control systemautonomously chooses a vehicle and automatically guides the vehicle totrack the ground target

2. Operator provides a planned route for a specific vehicle before thevehicle is launched . . . the vehicle follows the pre-planned route

3. Same as #2 but operator is allowed to change to a different plannedroute post launch (e.g., ability to change missions)

4. Control based on a vector-based decision process (e.g., vehicle willhead in a predetermined direction at speed x, altitude y, etc. . . .then turn based on new vector input information

5. Remote Directional Control (RDC) control (e.g., flying directionallysuch as with a multi-directional joystick input mechanism . . . withautonomous safety nets that do not let the operator aerodynamicallystall, over-steer, overbank, or otherwise compromise flight of thevehicle)

6. Full Manual Control (remote commands which directly reach the controlsurfaces un-compensated or conditioned)

Accordingly, the control systems of the present invention enable anoperator to move in and out of a range of different control modesselected from a broad control spectrum including everything fromautomated mission planning to direct control, with many available modesin between. Modes other than the six listed above are certainly withinthe scope of the present invention.

In accordance with one embodiment, the control system architecture ofthe present invention is flexible enough to support implementation ofcommercial-off-the-shelf (COTS) components to enable additional systemsub-components and corresponding control functionality. For example,software products for automatic route planning are commerciallyavailable an can be implemented in the context of the described controlsystem and architecture. For example, OR Concepts Applied (ORCA) ofWhittier, California provides at least one software product for routeplanning such as their “ORCA Planning & Utility System” (OPUS). This isbut one example of a software component that can be utilized to extendthe functionality of the broader control system. In accordance with oneembodiment, while programs such as OPUS are configured to generate aroute plan, the configuration of the control structure of the presentinvention (described in relation to FIGS. 3 and 4) will ensure that agenerated plan is optimized for the relevant vehicle (e.g., the plan isfiltered through command generator 404 and autopilot 406 before vehiclecontrol is directly impacted).

It should be noted that while FIG. 3 shows manual commands being enteredbelow the autopilot component 322, this is not necessarily the case.With reference to FIG. 4, in accordance with one embodiment of thepresent invention, when an operator chooses a manual control mode,manual instructions are translated into corresponding accelerationcommands. In accordance with one embodiment, the trajectory commands areprocessed by the autopilot component 406 such that, for example, whenthe operator lets go of the stick the vehicle will continue on arelatively straight and balanced path.

The present description, including FIGS. 3 and 4, has been described inthe context of a system that incorporates an autopilot componentconfigured to operate in accordance with commands expressed asacceleration-based descriptors of motion. It should be noted that anyother commands and corresponding autopilot system can be utilizedwithout departing from the scope of the present invention. For example,component 404 (FIG. 4) can be configured to generate commands in theform of bank-to-turn thrust values, skid-to-turn values, velocity-basedvalues, or any other descriptor of motion. Accordingly, autopilotcomponent 406 is generally a modular component that can be configured tosupport any of a wide variety of directional command structures anddescriptors of motion. Examples of autopilot systems within the scope ofthe present invention include, but are not limited to, bank-to-turnautopilots, skid-to-turn autopilots, and the like.

Accordingly, the present invention provides a hierarchical controlsystem and architecture that incorporates a broad range ofuser-selectable control modes representing variable levels of autonomy.A unified autopilot is provided to process available modes and modetransitions. An intelligence synthesizer is illustratively provided toassist in resolving functional conflicts and transitioning betweencontrol modes, although certain resolutions and transitions can beincorporated directly into the functional sub-components associated withthe different control modes and functions. In accordance with oneembodiment, all modes and transitions are funneled through anacceleration-based autopilot system. Accordingly, control commands andtransitions are generally reduced to an acceleration vector to beprocessed by the centralized autopilot system.

In accordance with one aspect of the present invention, a translationlayer is included to enable specialized control support for a given setof autopilot and vehicle control systems. In other words, thetranslation layer receives acceleration vectors (or some other output)and translates them into control instructions that are acceptable for aparticular vehicle's autopilot and control system. The translation layeressentially enables the control architecture and structures of thepresent invention to be adapted for any vehicle's autopilot system. Forexample, in accordance with one embodiment, a vehicle that incorporatesa control system that includes flight path angle-based trajectorycontrol can be enhanced with the significant variable autonomy controlfeatures of the present invention. The translation layer is configuredto receive an input and translate it into whatever commands arenecessary to support a given vehicle. It should also be noted it is notrequired that the translation layer input be in the form of anacceleration vector (e.g., it could be a velocity representation, etc.).

FIG. 5 is a diagrammatic block representation of a translation layerembodiment of the present invention. As is indicated by block 502,acceleration vectors are passed to a translator 504. Translator 504translates the acceleration vectors into a format appropriate for agiven autopilot system 506. As is indicated by block 508, the translatedcontrol instructions are utilized for vehicle control. Without departingfrom the scope of the present invention, the software support for thetranslation layer can be implemented in association with a groundstation system and/or an on-board vehicle control system.

In accordance with one embodiment, through implementation of atranslation layer, the control systems of the present invention employ ageneralized high-bandwidth autopilot interface design that can beapplied to a variety of air vehicles from conventional statically stabletail control airframes to high performance, statically unstable,tail-less combat vehicles or neutrally stable cruise missiles.

IV. System Architecture

In accordance with one aspect of the present invention, the describedVACS architecture and associated hierarchical control structure areimplemented in the context of two basic facilitating interfacecomponents: a ground control station interface and an airborne systeminterface. FIG. 6 is a schematic representation of top-level hardwareand software objects associated with each interface (labeled interface602 and 604, respectively). Interfaces 602 and 604 are linked to oneanother by a datalink 605. Datalink 605 is illustratively acommunications link that enables remote communication between the groundstation interface and the vehicle interface. All known methods forimplementing such a datalink are within the scope of the presentinvention.

The ground system interface 602 includes a centralized command andcontrol component 606. Component 606 is illustratively configured toprovide an operator with a user control interface. Through theinterface, with the aid of a video display component 614, component 606provides the operator with image data that is received by a missionsensor that is part of the vehicle's on-board payload. Through theinterface, with the aid of a vehicle status display 616, component 606provides the operator with control settings, warnings or other relevantvehicle status information. Through the user interface, with the aid ofa map display 610, component 606 provides the operator with a real timemap display that shows a vehicle's location relative to a map. A missionevaluation component 612 performs mission analysis and influencescommand and control component 606 as necessary depending on a givenimplementation. External interface 618 provides a means forcommunication with external sources such as, but not limited to,maintenance training equipment that provides logistics support for anyof a wide variety of maintenance training equipment. Component 606 isillustratively configured to receive and respond to inputs received fromthe operator through control input devices 608. Component 606communicates through datalink 605 with an executive component 652associated with airborne system interface 604. In this way, the operatoris able to control the vehicle at least with regard to flightcharacteristics and payload operations. Also, component 606 receivesdata from executive component 652 as necessary to support various systemfunctionalities (e.g., component 606 receives navigation data fromcomponent 652 for any of a wide variety of functions, for example, forsupplying an indication of aircraft location relative to map display610).

The executive component 652 is configured at least to process commandsand information received from command and control component 606. Severalcomponents are configured to support the functionality of executivecomponent 652, particularly with regard to flight control andmanagement. An atmosphere component 656 processes characteristics of thevehicle's surroundings as necessary at least to support the execution ofmanual and automated flight control decisions. A guidance component 658processes operator inputs, as well as automated and data inputs, inorder to facilitate flight control of the aircraft. A navigationcomponent 662 facilitates the collection and provision of datapertaining to aircraft location. Autopilot component 654 receives flightcontrol commands, processes the commands (e.g., makes adjustments toensure stable flight patterns), and passes commands to actuator controlcomponent 668 and engine control component 666 as necessary for flightcontrol execution. Vehicle management component 660 could have any of avariety of functions but illustratively at least coordinates andorganizes flight control sensor inputs. Payload control component 664manages the vehicle payload and facilitates the execution of payloadcommands received from the operator.

FIG. 7 is a schematic diagram illustrating an interface system similarto that illustrated in FIG. 6 but adapted for multiple vehicles. Groundsystem interface 702 is illustratively the same or similar to interface602 shown in FIG. 6. In order to simplify the illustration of interface702, only components 606, 608, 610, 614 and 616 are included. Any of theother components of interface 602 could be included without departingfrom the scope of the present invention. Other or different componentscould be included without departing from the scope of the presentinvention.

Ground system interface 702 includes one component that interface 602did not. Interface 702 includes a synthetic visuals component that isconfigured to provide the operator with a relatively real-time displayof a synthetically generated depiction of the vehicle and/or itsenvironment. The concept of synthetic visual display represents anembodiment of the present invention and will be described in greaterdetail below.

With further reference to FIG. 7, in accordance with one aspect of thepresent invention, communication between ground system interface 702 andan airborne system interface 730 is through a communications interface710 (e.g., a SLIP router) (in place of the simplified “datalink”illustrated in FIG. 6). Router 710 works in conjunction with a radio 712to transfer commands and flight information in a distributed manner to aplurality of radios 714-718. Each radio 714-718 is associated with adifferent executive component (e.g., components 720-724) located onboard a separate vehicle. Each vehicle's executive component isillustratively configured in a manner that is the same or similar tocomponent 652 illustrated in FIG. 6. As is shown in FIG. 7, eachexecutive component 720-724 includes components 652, 666, 668, 664, 662,654 and 658. Other or different components could be included withoutdeparting from the scope of the present invention.

V. Dynamic Control Schemes

FIG. 8, in accordance with one aspect of the present invention, is aschematic diagram representing a vehicle control scheme that supportsimplementation in the context of the described VACS architecture andcontrol structure. It should be emphasized that any form of autopilotcontroller (e.g., classical, optimal, robust, non-linear, or adaptive)can be employed without departing from the scope of the presentinvention, and without affecting the system architecture or operatorcontrol policies.

In accordance with the illustrated control scheme, operator inputs 802are provided to vehicle management software 804. Management software 804is configured to support an illustrative three different classes ofcontrol and corresponding operator inputs. The first class isrepresented by block 806, which is labeled energy optimal trajectory.Control modes of this type involve controlling the vehicle in asubstantially automated manner so as to maintain a preferred ordesignated trajectory while expending a relatively minimized amount ofenergy (e.g., to conserve potential energy). The second class isrepresented by block 808, which is labeled autonomous path control.Control modes of this type involve controlling the vehicle in asubstantially automated manner so as to maintain a flight control paththat is mission oriented and, optionally, selected and/or modified bythe operator. The third class is represented by block 810, which islabeled line-of-sight slave commands. As has been described, controlmodes of this type generally involve controlling the vehicle basedprimarily on manipulation of a visual sensor. The third class isrepresented by block 812, which is labeled remote directional commands.Control modes of this type have been previously described herein andgenerally involve, in one embodiment, controlling the vehicle based onsimplified directional commands with reliance on automation to determineappropriate execution parameters.

A switch 814 represents a selection of one of the different controlclasses based, for example, on a control mode selection that correspondsto an operator input 802. The switch 814 is notionally represented by asimple switch but is illustratively embedded in the more complexIntelligence Synthesizer processing architecture. Once a connection witha control class/mode has been established, subsequent correspondingvehicle control commands are translated through bank-to-turn and thrustcontrol component 816 (e.g., corresponding acceleration vector commandsare generated). Additional data derived from an air-data sensor source818 and/or software 804 is fed into the control process as necessary.The output of control component 816 is adjusted at component 820 (e.g.,autopilot adjustments) in order to compensate for deviations from theoriginal control command. As is illustrated, information fromcommercial-off-the-shelf integrated components 822 (e.g., coordinateinformation from GPS/IMU/NAV systems) can be fed into the determinationof actual deviations as necessary, and can also be utilized by software804 for any purpose such as but not limited to route planning. Followingadjustments for deviations, box 824 represents adjustments for airframestabilization (e.g., autopilot adjustments).

Following the steps associated with boxes 816, 820 and 824, box 826represents the step wherein control commands are actually executed andvehicle control surfaces and engine dynamics are actually manipulatedbased on the commands. Following execution of the commands, sensorsassociated with air-data sensor 818 and integrated components 822 returndata to points upstream in the process such that additional adjustmentscan be made if necessary (e.g., necessary to keep the vehicle on trackwith a desired route or necessary to keep the vehicle from stalling,crashing, etc.). As is indicated at 830, inertial dynamics are processedfollowing command execution. This information is passed along to camerastabilization and pointing component 840 such that adjustments can bemade if necessary to stabilize a camera, such as a gimbal-mounted camerautilized to support line-of-sight slave commands 810. Adjustments can bemade to the camera configuration based on relative geometry in order tokeep the camera relatively stable. Information input 832 represents aninput of target location information that enables the camera to focus onand follow a target.

There are several features and extensions of the described controlapproach to highlight:

-   1. In accordance with one aspect of the present invention, a library    of robust mathematical guidance algorithms (examples of which are    described later in the present description as embodiments of the    present invention) are employed to accommodate remote operator    command insertion at every level of flight control to address not    just the flight control problem but also flight management. This    design approach provides simplified manual control modes that enable    a relatively unskilled operator with minimal training to control the    vehicle.-   2. In accordance with another aspect of the present invention, the    payload sensor control is integrated into the guidance loop to    provide a control mechanism that shifts the operator's focus from    vehicle control to sensor control, without concern of the vehicle    flight profile. This control mechanism also facilitates the    introduction of a virtual control interface bringing immersive    control techniques to the airborne surveillance and reconnaissance    arena.-   3. An intuitive human-system interface (described in other sections    below) offers an interface with which operators can be trained to    execute a successful vehicle mission in a matter of hours or days as    opposed to weeks, months, or years.-   4. An intuitive, real-time mission planning capability is built into    the ground control station software to support real-time route    editing and vehicle mission retasking.-   5. The system enables real-time mission assessment such that the    operator can make rapid and precise real-time mission updates, as    dictated by higher level operational needs that change continuously    within a dynamic environment (e.g., battle environment).

In accordance with one aspect of the present invention, to enable asimplified manual control concept, the controller structure isimplemented such that the operator can have direct control of threeouter-loop states: airspeed (u), turn rate ({dot over (ψ)}) and altituderate ({dot over (h)}). To satisfy the requirements of fully autonomousflight, it is generally desired to close the outer loop around a fixedpath that is defined by preprogrammed waypoints. Analysis of the problemshows that both requirements (simplified manual and fully autonomouscontrol) could be satisfied with a single control loop structure.

In accordance with one aspect of the present invention, an improvedcontrol loop structure is provided. FIG. 9 is a control diagramrepresenting a general integrated guidance loop structure. Box 902represents operator input and box 904 represents gain or mapping frominput to autopilot. Together, boxes 902 and 904 represent an operatorcommand insertion point, for example for the simplified manual controlmode herein referred to as Remote Directional Response (RDR) or RemoteDirectional Command (RDC). Box 910 represents a waypoint guidance input.Box 912 represents pre-filtering adjustment to input 910 to maintain aproperly conditioned signal with desirable steady-state properties. Box914 represents a gain adjustment to input 910 to compensate for commanderror. Box 916 represents a feedback loop providing an adjustment forphugoid dampening. Box 918 represents autopilot controllerfunctionality. Box 920 represents the airframe plant itself (e.g., thevehicle and associated actuators actuated in response to the controlinput). Finally, box 922 represents integrals of the first dynamicstates, thus completing the plant dynamics model.

A switch 906 is inserted between the autopilot 908 and guidance systemthereby enabling the operator to command the autopilot 908 directly. Theswitch 906 is notionally represented by a simple switch but isillustratively embedded in the more complex Intelligence Synthesizerprocessing architecture. An example of operator commanded autopilotcontrol is horizontal steering. For horizontal steering, the operator'scontrol stick commands are mapped to horizontal turn rate commands. Theguidance software illustratively gains the turn rate command by thecurrent vehicle inertial velocity and feeds this term to the autopilot.In the vertical channel, the operator control stick commands are mappedto an altitude rate. The guidance software converts this command into aflight path angle command and computes a flight path followingacceleration command that feeds the autopilot. In accordance with oneembodiment, when the operator “lets go of the stick”, the flightsoftware simply commands the vehicle to fly straight and level at thecurrent altitude and current heading.

As FIG. 9 demonstrates, the general form of the outer loop guidancealgorithm is a second order inertial path controller. The correspondingform of the autopilot utilizes an acceleration command input. Thus, theincorporated autopilot structure is an acceleration command autopilot inthe pitch and yaw axis and a bank angle command autopilot in the rollaxis. It should be noted that other gain scheduling techniques andacceleration autopilots are within the scope of the present invention.Different autonomous vehicles will illustratively incorporate differentgain scheduling techniques and autopilots, the VACS architecture andcontrol structures being conveniently adaptable by one skilled in theart to accommodate such variations. A list of autopilot systems that canbe accommodated includes, but is not limited to:

-   1. Linear classical control designs using pole-placement gain    scheduling techniques-   2. Non-linear control design using dynamic inversion-   3. Non-linear adaptive control design-   4. LQR (optimal) control design-   5. Loop shaping control design

In one embodiment, as was alluded to in relation to FIG. 5, atranslation layer can be implemented to translate a given control output(e.g., an acceleration based command) to an alternative form asnecessary to accommodate any of the above five or other autopilotsystems.

VI. Coordinate Frame Definitions

In order to support description of specific control modes and guidancemethods, a few different standard coordinate frame definitions andtransformations will now be described.

FIG. 10-1 is a diagrammatic representation of an Earth Centered EarthFixed (ECEF) coordinate frame definition. The ECEF reference frame isoriented with its origin at the earth's center. The x and y axes lie inthe equatorial plane with the x-axis passing through the GreenwichMeridian. The z-axis is normal to the x-y plane and passes through theNorth Pole.

FIGS. 10-2 and 10-3 are diagrammatic representations of a Geodeticcoordinate frame definition. The geodetic coordinate frame defines thelines of latitude and longitude along the earth's surface. Geodeticlatitude is the angle between the equatorial plane and the normal to thesurface of the ellipsoid. Geodetic longitude is the angular rotationrelative to the ECEF x-axis in the equatorial plane. Geodetic altitudeis the elevation above the ellipsoid surface.

A coordinate reference frame definition that is not illustrated is thelocal vertical reference frame, which is oriented with its origin at apoint along the earth's surface defined by an angular rotation from theECEF frame (latitude and longitude) and an altitude, h, above theearth's surface. This frame's z-axis is normal to the local tangent ofthe ellipsoid. The x-y plane lies normal to the z-axis and parallel tothe local horizon.

FIG. 10-4 is a schematic representation of a body reference frame. Thebody reference frame has its origin at the vehicle center of gravity.The y-axis extends out of the right wing of the vehicle, the x-axisextends out the nose of the vehicle, and the z-axis is positive downpassing normal to the x-y plane.

Certain embodiments of the present invention involve coordinate frametransformations. For example, a function can be applied to transformgeodetic coordinates to ECEF coordinates. In accordance with oneembodiment of such a transformation, coordinate waypoints are passedinto the UAV flight computer in geodetic coordinates (latitude (λ),longitude (l) and altitude (h), Earth semi-major axis (a_(E)),eccentricity e). These waypoint locations are then transformed to ECEFcoordinates utilizing a function such as:

$\begin{matrix}{{\overset{\rightharpoonup}{P}}_{ECEF} = \begin{Bmatrix}{\left( {\frac{a_{E}}{\sqrt{1 - {e^{2}{\sin^{2}(\lambda)}}}} + h} \right){\cos(\lambda)}{\cos(l)}} \\{\left( {\frac{a_{E}}{\sqrt{1 - {e^{2}{\sin^{2}(\lambda)}}}} + h} \right){\cos(\lambda)}{\sin(l)}} \\{\left( {\frac{a_{E}\left( {1 - e^{2}} \right)}{\sqrt{1 - {e^{2}{\sin^{2}(\lambda)}}}} + h} \right){\sin(\lambda)}}\end{Bmatrix}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

Similarly, ECEF coordinates can be transformed into local verticalcoordinates. In accordance with one embodiment of such a transformation,the guidance error equations are formulated in the ECEF reference frame,then converted to the local vertical reference frame for computation ofthe guidance commands. The ECEF to local vertical transformation matrixcan be defined as:

$\begin{matrix}{T_{E}^{L} = \begin{bmatrix}{{- {\sin(\lambda)}}{\cos(l)}} & {{- {\sin(\lambda)}}{\sin(l)}} & {\cos(\lambda)} \\{- {\sin(l)}} & {\cos(l)} & 0 \\{{- {\cos(\lambda)}}{\cos(l)}} & {{- {\cos(\lambda)}}{\sin(l)}} & {- {\sin(\lambda)}}\end{bmatrix}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

Local vertical guidance commands can then be transformed into the bodyreference frame for input to the autopilot through the transformationmatrix (pitch angle Θ, yaw angle Ψ, roll angle Φ):

$\begin{matrix}{T_{B}^{L} = \begin{bmatrix}{\cos\;\Psi\;\cos\;\Theta} & {\sin\;\Psi\;\cos\;\Theta} & {{- \sin}\mspace{11mu}\Theta} \\\begin{matrix}{{\cos\;\Psi\;\sin\;{\Theta sin\Phi}} -} \\{\sin\;\Psi\;\cos\;\Phi}\end{matrix} & \begin{matrix}{{\sin\;\Psi\;\sin\;{\Theta sin\Phi}} +} \\{\cos\;{\Psi cos}\;\Phi}\end{matrix} & {\cos\;{\Theta sin}\;\Phi} \\\begin{matrix}{{\cos\;\Psi\;\sin\;{\Theta cos\Phi}} +} \\{\sin\;{\Psi sin}\;\Phi}\end{matrix} & \begin{matrix}{{\sin\;\Psi\;\sin\;{\Theta cos\Phi}} +} \\{\cos\;{\Psi sin}\;\Phi}\end{matrix} & {\cos\;{\Theta cos}\;\Phi}\end{bmatrix}} & {{Eq}.\mspace{14mu} 3}\end{matrix}$VII. Navigator

In another aspect of the present invention, vehicle state information isprovided by a component herein referred to as the navigator component.Navigator components are known in the art to provide information suchas, but not limited to, position, velocity, acceleration, angularposition and/or angular velocity associated with the vehicle. Some knownnavigator components incorporate sensor devices such as, but not limitedto, a three-axis inertial measurement unit, a GPS receiver, and/orstrap-down equation software, and Kalman filter used to estimate the IMUsensor error.

Information output from navigator components is utilized for any of avariety of purposes. For example, the accelerations, angular rates andother similar outputs are illustratively fed into an autopilot system insupport of stability-enhancing processes. Position, velocity, angularposition and other similar outputs are used by the guidancefunctionality to aid in decision-making such as, but certainly notlimited to, path-regulation.

VIII. Guidance

In another aspect of the present invention, a guidance function isresponsible for generating autopilot commands that, when executed,achieve a particular guidance objective. Guidance objectives aredesigned to satisfy operator interface and mission control requirementsand include functions such as, “regulate to a preprogrammed inertialpath,” “go to and monitor a specified target coordinate,” “execute anoperator commanded programmed maneuver,” “slave to an operator commandedsensor stare command,” etc.

FIG. 11, in accordance with one aspect of the present invention, is aschematic block diagram demonstrating a basic flow structure for thevarious flight mode levels and identifying underlying guidance lawscalled by the flight management software component. There are anillustrative four levels of operational modes within the vehiclemanager: flight mode 1102, flight sub-mode 1104, guidance mode 1106, andguidance sub-mode 1108.

Flight mode 1102 includes three different functions, namely, take-off1110, inflight 1112, and landing 1114. For take-off 1110, flightsub-mode 1104 includes four primary functions, namely, taxi 1116,throttle-up 1118, ground roll 1120 and climbout 1122. When these foursub-mode functions have been executed, guidance mode 1124 (flywaypoints) is executed. In that regard, waypoint guidance law 1134 isexecuted including sub-modes 1126 (waypoint capture) and 1128 (legregulation).

When the flight mode is inflight 1112, the operator can select betweenflight sub-modes 1136 (autonomous control) and 1140 (manual control).One selectable option for autonomous control is the fly waypoints 1124guidance mode in accordance with waypoint guidance law 1134. Anotherselectable autonomous control mode is loiter guidance mode 1142, whichis executed in accordance with loiter capture guidance sub-mode 1130 andorbit guidance sub-mode 1132 being subcomponents of loiter guidance law1144.

Options for manual control 1140 include RDC guidance mode 1146,LOS-slave mode 1148 and hybrid control mode 1150. Each of these manualcontrol modes are related to guidance sub-modes 1152 (command following)and 1154 (reference hold), which are related to flight path guidance law1156. It should be noted that guidance modes and guidance sub-modes canbe combined as indicated to enable a biased pursuit guidance law 1158 inaccordance with one aspect of the present invention.

The library of outer-loop guidance modes support both autonomous controlas well as simplified manual control. Guidance laws that are within thescope of the present invention and are exploited by the vehicle managerinclude, but are not limited to, waypoint guidance, loiter guidance,line-of-sight slave control guidance and remote directional commandguidance. Various guidance modes invoke these guidance laws to achievediverse mission objectives. For example, loiter guidance is a guidancelaw invoked by several difference guidance modes including, but notlimited to, programmed route guidance, park guidance, observation pointguidance, and moving target tracking guidance.

In one embodiment, the operator at any point during a mission caninterrupt the vehicle management software component. The component willillustratively process the operator's inputs and perform the appropriateaction, which may include entering a manual control mode, entering anoperator specified orbit pattern, or updating and executing a plannednavigation route.

The control system design and architecture of the present inventionenables a single operator to seamlessly transition between varyinglevels of control autonomy for an individual vehicle. Such controlcapability even enables the single operator to effectively manage andcontrol a team of vehicles. In another aspect of the present invention,to support such functionality, a gradient control scheme is provided andutilizes on-board trajectory synthesis techniques to establish aninertial reference trajectory to which a vehicle is regulated. Thegradient control approach is predicated on the use of accelerationfeedback in the pitch channel autopilot. As has been alluded to,however, the solution is extensible to platforms that do not employacceleration feedback, for example through implementation of amathematical translation or transformation from the acceleration commandto the native state command accepted by the native autopilot. Hence, anacceleration autopilot is not implicitly required to adequately satisfythe guidance objectives generated by the presently described variableautonomy control algorithms.

Kinematics provides a motivation for acceleration based vehicle control.Both rectilinear and relative general plane equations of motion relateposition and velocity states (translational or angular) to accelerationthrough mathematically tractable differential equations. The followingequations are examples of translational and rotational differentialequations formulated as guidance laws for typical navigation and homingguidance:{right arrow over (a)} _(cmd)=ω² Δ{right arrow over (P)}+2ζωΔ{dot over({right arrow over (P)}+{right arrow over (g)}  Eq. 4

where

ω=guidance law natural frequency

Δ{right arrow over (P)}=guidance position error

ζ=guidance law damping ratio

Δ{dot over ({right arrow over (P)}=guidance velocity error

{right arrow over (g)}=gravity

(translational−waypoint guidance)R{umlaut over (λ)}−2V{dot over (λ)}=−NV{dot over (λ)}≡−a _(cmd)  Eq. 5

where

R=relative range to target)

{umlaut over (λ)}=line-of-sight accleration

V=closing velocity to target

{dot over (λ)}=line-of-sight rate

N=guidance law gain

(rotational−proportional navigation)

Such equations are consistent with fundamental principals of autonomousvehicle guidance and control. The theory behind the autonomy controlsystems of the present invention illustratively capitalizes on theproperties of the differential equations that formulate the desiredacceleration commands. Given that the underlying equations of motionthat describe physical motion of air vehicles are continuous functionsoperating over a set of real variables from “negative infinity topositive infinity” (no discontinuities in the function), then it servesthat the derivatives of these functions are continuous. Hence,rectilinear acceleration commands can be generated to regulate velocityreference trajectories (first order control law—acceleration is thefirst derivative of velocity) or position reference trajectories (secondorder control law—acceleration is the second derivative of position). Itcan therefore be shown that the transition between derivative controlmodes is stable, assuming the gains for each corresponding controlscheme provide a stable response. Closed-loop stability over modetransitions is then eliminated as a concern and, hence, the transitionbetween control modes is essentially seamless. The following equationsillustrate this principal:

-   Gradient Control Scheme: Eq. 6-   R=Input (state to be controlled)-   U=Control signal

${U = \frac{\partial^{n}R}{\partial t^{n}}},$

-   n is number of derivatives between input and control signal-   Example Applications: Eqs. 7 & 8-   Case 1: Second-Order-   R=Reference path for waypoint guidance (P)-   U=Acceleration command (a)

$\begin{matrix}{a = \frac{\partial^{2}P}{\partial t^{2}}} \\{\underset{Laplace}{=}{\left( {{As}^{2} + {Bs} + C} \right){P(s)}}} \\{= 0} \\{\underset{Discrete}{\Rightarrow}{\delta\;\overset{¨}{P}}} \\{= a} \\{= {{2{\zeta\omega\delta}\;\overset{.}{P}} + {\omega^{2}\delta\; P}}}\end{matrix}$

-   Case 2: First-Order-   R=Flight path velocity command

$\left( {\gamma \approx \frac{V_{up}}{\overset{\rightharpoonup}{V}}} \right)$

-   U=Acceleration command (a)

$a = {\frac{{\overset{\rightharpoonup}{V}}{\partial\gamma}}{\partial t}\underset{Laplace}{=}{{{\overset{\rightharpoonup}{V}}\left( {{As} + B} \right){\gamma(s)}} = {{0\underset{Discrete}{\Rightarrow}{{\overset{\rightharpoonup}{V}}\overset{.}{\lambda}}} = {a = {\frac{\overset{\rightharpoonup}{V}}{\tau}{\delta\gamma}}}}}}$

The above examples illustrate waypoint guidance (second order) andflight path angle guidance (first order) laws. The guidance laws canregulate to any mathematically tractable reference path from whichposition and/or velocity and orientation errors between the vehicle andthe path are computed. The reference paths can be generated apriori by amission planner (waypoint route, for example) or synthesizedautonomously by on-board flight control software to achieve a high levelobjective commanded by an operator (autonomous landing terminaltrajectory, for example). This approach provides a control scheme inwhich an operator can issue commands of varying levels of autonomywithout regard for the closed-loop vehicle stability during modetransitions. Applying this scheme, in accordance with one embodiment ofthe present invention, a baseline set of guidance laws alluded to inFIG. 8 (waypoint guidance, flight path angle guidance, line-of-sightrate guidance, and sensor-slave guidance) provide a core guidance lawtoolbox upon which the variable autonomy control system described hereinis built. Higher level software processing functions then interpretoperator commands, sensor inputs, and database inputs and translatethese inputs into executable guidance laws that the control system thenacts on. In another aspect of the present invention, this design enablesrobust higher level autonomous control functions within the describedVACS framework. Such functions illustratively include, but are notlimited to, functions for ground collision avoidance, air collisionavoidance (“see & avoid”), ground moving target tracking and following,formation flying (multiple vehicles), and autonomous landing. Autonomousguidance algorithms designed to support the system will now be describedin greater detail.

A. Waypoint Guidance

In accordance with one aspect, as is indicated by block 132 in FIG. 1,one provided control mode enables a waypoint guidance control mode. Inone embodiment of waypoint guidance, guidance error computations areperformed in the ECEF reference frame then rotated into the localvertical reference frame prior to being addressed in the guidance law.The error computations are illustratively separated between a waypointleg regulation phase and a waypoint leg transition phase. Whileinertially guiding to a waypoint leg, the guidance errors areillustratively derived by first forming a vector triangle between thevehicle (i.e., the UAV) and the two waypoints that make up the waypointleg.

FIG. 12 is a schematic diagram demonstrating waypoint guidance errorcalculation in accordance with one embodiment of the present invention.The position error (Δ{right arrow over (P)}) and the velocity error(Δ{right arrow over (V)}) can be computed from the vector triangle shownin the Figure. For example,

$\begin{matrix}{{\overset{\rightharpoonup}{B} = {{\overset{\rightharpoonup}{P}}^{UAV} - {\overset{\rightharpoonup}{P}}^{{WP}\; 1}}}{{\overset{\rightharpoonup}{R}}_{LEG} = {{\overset{\rightharpoonup}{P}}^{{WP}\; 2} - {\overset{\rightharpoonup}{P}}^{{WP}\; 1}}}{{\overset{\rightharpoonup}{u}}_{LEG} = \frac{{\overset{\rightharpoonup}{R}}_{LEG}}{{\overset{\rightharpoonup}{R}}_{LEG}}}{{\Delta\;\overset{\rightharpoonup}{P}} = {\overset{\rightharpoonup}{B} - {\left( {\overset{\rightharpoonup}{B} \cdot {\overset{\rightharpoonup}{u}}_{LEG}} \right){\overset{\rightharpoonup}{u}}_{LEG}}}}{{\Delta\;\overset{\rightharpoonup}{\overset{.}{P}}} = {{\overset{\rightharpoonup}{V}}_{I} - {\left( {{\overset{\rightharpoonup}{V}}_{I} \cdot {\overset{\rightharpoonup}{u}}_{LEG}} \right){\overset{\rightharpoonup}{u}}_{LEG}}}}} & {{Eq}.\mspace{14mu} 9}\end{matrix}$

These Eq. 9 calculations provide the solution for horizontal channelguidance errors. A correction must be made, however, to the verticalchannel guidance error to account for the earth's curvature.

FIG. 13 is a schematic diagram demonstrating that considerable altitudeerrors can be introduced by failing to account for the earth'scurvature. Since the guidance errors are ultimately rotated into thelocal vertical coordinate frame, a simple solution exists to performingthe great circular arc correction. Through recognizing the fact thateach waypoint altitude is stored as an ellipsoidal altitude and that thecurrent vehicle ellipsoidal altitude is always available from thenavigation solution, the curvature problem can be mathematicallyeliminated from the altitude error calculation with instantaneous ECEFto local vertical transformation. Simply stated, the altitude error iscomputed as the error between the current vehicle ellipsoidal altitudeand the geodesic line connecting the two waypoints. Although the path isa curved path in the ECEF frame, the instantaneous rotation to the localvertical frame linearizes the problem.

FIG. 14 is a schematic diagram demonstrating altitude error calculationin the form of a curvature correction for the vertical guidance error.Using the nomenclature in FIG. 14, the local vertical altitude error(accounting for the earth's curvature) is illustratively computed as:

$\begin{matrix}{{\Delta\; H} = {H_{v} - H_{1} - {\frac{x}{R_{G}}\left( {H_{2} - H_{1}} \right)}}} & {{Eq}.\mspace{14mu} 10}\end{matrix}$

The local vertical velocity error is calculated as:Δ{dot over (H)}={dot over (H)} _(V) −|{right arrow over (V)}_(i)|sin(γ_(D))  Eq. 11

In accordance with one aspect of the present invention, waypoint legtransition logic is premised on a desire to transition waypoint legswhen the horizontal acceleration required to drive the vehicle onto thenext waypoint leg heading in the desired waypoint leg direction is aminimum. This requirement is achieved mathematically by transitioningwaypoint legs when the dot product of the horizontal position error(relative to the next waypoint leg) and the horizontal accelerationerror (relative to the next waypoint leg) is zero. Since it is notguaranteed that this dot product will be identically zero on any givencompute cycle, the transition occurs when the sign of this dot productchanges from positive to negative.

FIG. 15 is a schematic diagram demonstrating the waypoint leg transitionissue with particular coordinate frames to be utilized in an algorithmdesigned to address the issue. The waypoint leg transition algorithmbegins by computing local vertical guidance errors (position andvelocity) and an acceleration command vector relative to the nextwaypoint leg in the same manner that these errors are computed relativeto the current waypoint leg. Next a rotation matrix between the localvertical reference frame (E, N) and the next waypoint leg referenceframe (Along, Across) is computed as follows:

$\begin{matrix}{\begin{Bmatrix}{Along} \\{Across}\end{Bmatrix} = {\begin{bmatrix}{\sin\left( \Psi_{leg} \right)} & {\cos\left( \Psi_{leg} \right)} \\{\cos\left( \Psi_{leg} \right)} & {- {\sin\left( \Psi_{leg} \right)}}\end{bmatrix}\begin{Bmatrix}E \\N\end{Bmatrix}}} & {{Eq}.\mspace{14mu} 12}\end{matrix}$

The local vertical to waypoint leg reference frame rotation matrix isillustratively denoted T_(L) ^(W). The position and acceleration errorsrelative to the next waypoint leg are then rotated into the nextwaypoint leg reference frame:Δ{right arrow over (P)}_(w)=T_(L) ^(w)Δ{right arrow over (P)}_(LV)Δ{right arrow over (a)}_(cw)=T_(L) ^(w){right arrow over (a)}_(cLV)  Eq.13

The waypoint leg transition illustratively occurs when ΔP_(Across)a_(c)_(Across) ≦0.

In accordance with one aspect of the present invention, an enhancedwaypoint guidance algorithm is applied to achieve improved pathregulation during 3D waypoint turns. Issues arise when two adjoiningwaypoint segments have different vertical and horizontal slopes,requiring the vehicle to “turn” in both the horizontal and verticalchannels. These two waypoint segments form a plane (‘two intersectinglines form a plane’). In accordance with one embodiment, the parametersfor this plane are computed and the vehicle is commanded to perform itsturn in that plane.

FIG. 16 is a schematic diagram demonstrating the concept of commandingthe vehicle to perform its turn in the derived plane. In accordance withone embodiment, the control law used during the 3D planar turn is:

$\begin{matrix}{{\overset{\rightarrow}{a}}_{cmd} = {{{- \frac{V^{2}}{R}}{\overset{\rightarrow}{U}}_{plane}} + {\omega^{2}\Delta\;\overset{\rightarrow}{P}} + {2{\xi\omega\Delta}\;\overset{\rightarrow}{V}} + {g\overset{\rightarrow}{U}p}}} & {{Eq}.\mspace{14mu} 14}\end{matrix}$

whereΔ{right arrow over (P)}={right arrow over (R)}+R_(turn){right arrow over(u)}_(plane)Δ{right arrow over (V)}=({right arrow over (V)}·{right arrow over(n)}_(plane)){right arrow over (n)}_(plane)+({right arrow over(V)}·{right arrow over (u)}_(plane)){right arrow over (u)}_(plane)

-   -   R_(turn)=Vehicle turn radius    -   {right arrow over (R)}=relative distance between vehicle and        turn center

The turn radius is illustratively vehicle dependent and the planarparameters (plane center location, plane normal vector, and plane unitvector) are all illustratively computed using basic analytical geometry.This algorithm is illustratively advantageous at least in that itpromotes generality for precision path control across a broad class ofUAV's.

The waypoint guidance system is illustratively organized as a linkedlist of events augmented with smooth turn and leg propagation logic ateach station. An event is illustratively, but not limited to, a waypoint, an orbit pattern, a payload command (e.g., point camera atlocation x) or some other event. This provides the capability to easilyedit the mission plan from the graphical display both during pre-flightmission planning and while the UAV is in the air. If the operatordiscovers an unknown hazard in the pre-planned flight-path, then he caneither “drag-and-drop” existing events or he can delete and insert newevents as necessary.

For illustrative purposes only, table 1 is provided as a samplecollection of event parameters.

TABLE 1 Event Type Waypoint, FIG. 8, racetrack, ellipse (circle isracetrack with equal length and width) Waypoint latitude Geodeticlatitude of waypoint or orbit pattern center Waypoint longitude Geodeticlatitude of waypoint or orbit pattern center Waypoint AltitudeEllipsoidal altitude of waypoint or orbit pattern center Waypoint SpeedSpeed setting at waypoint location Orbit pattern length Length ofdesired orbit pattern Orbit pattern width Width of desired orbit patternOrbit pattern Rotation angle of orbit pattern (relative to trueorientation North) Number of orbit Desired number of orbit laps lapsTime in orbit Desired time to maintain orbit pattern (overrides orbitlaps if greater than minimum threshold) Orbit pattern Offset vector oforbit pattern center from known center offset target location

B. Loiter Control

In accordance with one aspect of the present invention, as is indicatedby block 134 in FIG. 1, one provided control mode enables an operator toloiter a vehicle over a given station, for example, to monitor a desiredsurveillance point. The system illustratively enables the operator toeither preprogram a set of orbit patterns embedded within a waypointroute or dynamically insert orbit patterns into an existing route inreal-time. The operator can illustratively set loiter parameters such aslength, width, and orientation (i.e., heading) of the orbit pattern witha simply controlled input operation (e.g., mouse controlledclick-and-drag operation on a 2D map displayed as part of the userinterface). In accordance with one embodiment, a set of relief orhand-off park modes is also provided in which the vehicle willautomatically enter into a default racetrack, a figure-8, or anelliptical orbit pattern upon command from the operator.

Accordingly, one embodiment of the present invention pertains to systemsupport for an elliptical orbit pattern. The system illustrativelyenables the operator to select an oval or a constant radius (circular)loiter pattern. In accordance with one embodiment, along with anoperator selectable offset vector for the loiter pattern centroid, theoperator is also illustratively provided with the capability to select aloiter pattern “heading” relative to north. For circular patterns thisoption has little value. For elliptical patterns, however, the latterselection option provides the operator with an ability to adjust aloiter pattern to fit virtually any desired geographic location, such asa country's border or a canyon.

In accordance with one aspect of the present invention, loiter guidanceis achieved through two basic guidance laws: 1) Biased pursuit guidancelaw used to drive the vehicle onto a desired loiter pattern(illustratively referred to herein as loiter capture); and 2) Ellipticalguidance law which serves as an inertial path controller designed toslave the vehicle to an elliptical loiter pattern (illustrativelyreferred to herein as loiter guidance).

FIG. 17, in accordance with one aspect of the present invention, is aschematic diagram defining parameters and coordinate frames used toconstruct the elliptical loiter guidance law. The desired surveillancepoint and ellipse center offset, semi-major axis, and semi-minor axisare either preprogrammed into the UAV flight software or input by theoperator real-time during a mission. Once the UAV captures the desiredloiter pattern, the loiter guidance law is invoked. The loiter guidanceerror equations are computed in the ellipse reference frame. This frameis defined as (x_(E),y_(E)) in FIG. 17. The transformation matrix fromthe local vertical reference frame to the ellipse reference frame(T_(LV) ^(E)) is computed as:

$\begin{matrix}{\begin{Bmatrix}x_{E} \\y_{E} \\z_{E}\end{Bmatrix} = {\begin{bmatrix}{\cos\left( \Psi_{E} \right)} & {- {\sin\left( \Psi_{E} \right)}} & 0 \\{\sin\left( \Psi_{E} \right)} & {\cos\left( \Psi_{E} \right)} & 0 \\0 & 0 & 1\end{bmatrix}\begin{Bmatrix}E \\N \\U\end{Bmatrix}}} & {{Eq}.\mspace{14mu} 15}\end{matrix}$

The transformation matrix from the ECEF frame to the ellipse frame isthen computed as:T_(ECEF) ^(E)=T_(LV) ^(E)T_(ECEF) ^(LV)  Eq. 16

The position of the vehicle is computed relative to the surveillancepoint in ellipse coordinates as follows:{right arrow over (P)} _(rel) ^(E) =T _(ECEF) ^(E)({right arrow over(P)} _(UAV) ^(ECEF) −{right arrow over (P)} _(S) ^(ECEF))  Eq. 17

-   -   where {right arrow over (P)}_(UAV) ^(ECEF)=ECEF UAV position        -   {right arrow over (P)}_(S) ^(ECEF)=ECEF surveillance point            location

Consistent with basic analytic geometry, the equation for an ellipse canbe written in parametric coordinates:x _(E) =x _(c) +b sin(t);y _(E) =y _(c) +a cos(t)  Eq. 18

Utilizing this relationship and assuming that the vehicle is near thedesired ellipse, the instantaneous ellipse parametric angle (t) iscomputed as

$\begin{matrix}{t = {\tan^{- 1}\left( \frac{a\left( {P_{{rel}_{x}}^{E} - x_{c}} \right)}{b\left( {P_{{rel}_{y}}^{E} - y_{c}} \right)} \right)}} & {{Eq}.\mspace{14mu} 19}\end{matrix}$

It is important to emphasize the assumption that the vehicle is near thedesired loiter pattern. This is the assumption that drives therequirement of a second guidance law (loiter capture) to guide thevehicle onto the ellipse. In accordance with one embodiment, “Near theellipse” is quantified in terms of relative heading and horizontalground distance. The guidance software is configured to consider thevehicle to be near the ellipse if the horizontal ground distance betweenthe vehicle and the ellipse surface is less than a predetermineddistance threshold (e.g., 0.1 nm) and the relative heading error betweenthe vehicle and the ellipse tangent is less than a predetermined angularthreshold (e.g., 10 deg.).

Having computed the instantaneous parametric angle, the desired vehicleposition is computed using the ellipse parametric equations:

$\begin{matrix}{{\overset{\rightharpoonup}{p}}_{D}^{E} = \begin{Bmatrix}{x_{c} + {b\;{\sin(t)}}} \\{y_{c} + {a\;{\cos(t)}}} \\0\end{Bmatrix}} & {{Eq}.\mspace{14mu} 20}\end{matrix}$

The desired heading in ellipse coordinates is then computed as:

$\begin{matrix}{\Psi_{D} = {{\tan^{- 1}\left( \frac{a^{2}\left( {P_{D_{x}}^{E} - x_{c}} \right)}{b^{2}\left( {P_{D_{y}}^{E} - y_{c}} \right)} \right)} - \pi}} & {{Eq}.\mspace{14mu} 21}\end{matrix}$

The associated desired inertial velocity vector is then computed:

$\begin{matrix}{{\overset{\rightharpoonup}{V}}_{D}^{E} = {T_{LV}^{E}\begin{Bmatrix}{{{\overset{\rightharpoonup}{V}}_{I}}{\sin\left( \Psi_{D} \right)}} \\{{{\overset{\rightharpoonup}{V}}_{I}}{\cos\left( \Psi_{D} \right)}} \\0\end{Bmatrix}}} & {{Eq}.\mspace{14mu} 22}\end{matrix}$

Note that a constant altitude loiter is illustratively assumed. Theguidance position and velocity errors in local vertical coordinates arecomputed as follows:Δ{right arrow over (P)} ^(LV) =[T _(LV) ^(E)]^(T)({right arrow over (P)}_(rel) ^(E) −{right arrow over (P)} _(D) ^(E))Δ{right arrow over (V)} ^(LV) =[T _(LV) ^(E)]^(T)({right arrow over (V)}_(I) ^(E) −{right arrow over (V)} _(D) ^(E))  Eq. 23

where {right arrow over (V)}_(I) ^(E)=Inertial velocity vector inellipse coordinates

An instantaneous radius of curvature (ρ) can be computed at each pointalong the ellipse. This curvature vector is normal to the ellipsetangent, which defines the heading to which the vehicle will align theinertial velocity vector. Because the vehicle is slaved to the ellipse,the instantaneous radius of curvature of the ellipse is identicallyequal to the instantaneous vehicle horizontal turn radius. Hence theellipse radius of curvature can be used to augment the guidance law, asit will provide the desired steady-state horizontal centripetalacceleration. The radius of curvature is computed as:

$\begin{matrix}{\rho = \frac{\left\lbrack {{b^{2}{\cos^{2}(t)}} + {a^{2}{\sin^{2}(t)}}} \right\rbrack^{3/2}}{ab}} & {{Eq}.\mspace{14mu} 24}\end{matrix}$

The desired centripetal acceleration command in local verticalcoordinates can then be computed as:

$\begin{matrix}{{\overset{\rightharpoonup}{a}}_{cent} = {\left\lbrack T_{LV}^{E} \right\rbrack^{T}\left( \frac{{\overset{\rightharpoonup}{V}}_{I}^{2}}{\rho} \right)\begin{Bmatrix}{- {\sin(\eta)}} \\{- {\cos(\eta)}} \\0\end{Bmatrix}}} & {{Eq}.\mspace{14mu} 25}\end{matrix}$

The local vertical acceleration command vector is computed as:{right arrow over (a)} _(c) ^(LV) ={right arrow over (a)} _(cent) −k_(p) Δ{right arrow over (P)} ^(LV) −k _(v) Δ{right arrow over (V)} ^(LV)−{right arrow over (g)} ^(LV) +k _(p) k _(FF) _(2,1) {right arrow over(V)} _(c)  Eq. 26

-   -   {right arrow over (V)}_(c)=[0 0 V_(c)]^(T)=Airspeed command    -   {right arrow over (g)}^(LV)=[0 0 −9.81]^(T)

This acceleration command vector is then processed through a translationlayer and/or is delivered to the autopilot system.

In accordance with one aspect of the present invention, the loitercapture algorithm is designed to drive the vehicle onto the desiredloiter pattern from any location outside of the planned pattern. Inaccordance with one embodiment, the loiter capture algorithmsimultaneously drives the vehicle onto the desired ellipse at thedesired heading utilizing the biased pursuit guidance law and theellipse tangent lines.

FIG. 18, in accordance with one embodiment, is a schematic chartdemonstrating that, for any point, P, outside of the ellipse there existtwo lines passing tangent to the ellipse and containing the point P. Thearrows in the figure indicate a desired direction of travel along theellipse. Although there are two tangent line solutions, accounting forthe desired direction of travel reduces the problem to one solution.Upon entrance into loiter capture, the guidance algorithm illustrativelysolves for the ellipse tangent line that will bring the vehicle onto theellipse headed in the desired direction of travel along the ellipse. Abiased pursuit guidance law is then illustratively used to control thevehicle along the computed tangent line.

In accordance with one embodiment, the position of the vehicle is firstcomputed relative to the loiter pattern center in ellipse coordinates asfollows:{right arrow over (P)} _(rel) ^(E) =T _(ECEF) ^(E)({right arrow over(P)} _(UAV) ^(ECEF) −{right arrow over (P)} _(S) ^(ECEF))−{right arrowover (P)} _(center)  Eq. 27where {right arrow over (P)}_(UAV) ^(ECEF)=ECEF UAV position

{right arrow over (P)}_(S) ^(ECEF)=ECEF surveillance point location

{right arrow over (P)}_(center)=ellipse center location relative tosurveillance point in ellipse cooridates

The tangent point on the ellipse is then computed:

$\begin{matrix}\begin{matrix}{x_{t} = \left\{ \begin{matrix}{- \frac{b\sqrt{y_{v}^{2} - a^{2}}}{y_{v}}} & {x_{v} = 0} \\{- \frac{b^{2}\left( {{- 1} + {\frac{1}{2}\frac{y_{v}\left( {{2\; b^{2}y_{v}} + {2\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}} \right)}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}}} \right)}{x_{v}}} & {x_{v} > 0} \\{- \frac{b^{2}\left( {{- 1} + {\frac{1}{2}\frac{y_{v}\left( {{2\; b^{2}y_{v}} - {2\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}} \right)}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}}} \right)}{x_{v}}} & {x_{v} < 0}\end{matrix} \right.} \\{\mspace{20mu}{y_{t} = \left\{ \begin{matrix}\frac{a^{2}}{y_{v}} & {x_{v} = 0} \\{\frac{1}{2}\frac{\left( {{2\; b^{2}y_{v}} + {2\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}} \right)a^{2}}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}} & {x_{v} > 0} \\{\frac{1}{2}\frac{\left( {{2\; b^{2}y_{v}} - {2\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}} \right)a^{2}}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}} & {x_{v} < 0}\end{matrix} \right.}}\end{matrix} & {{Eq}.\mspace{14mu} 28}\end{matrix}$

where x_(v)=P_(rel) _(x) ^(E)=vehicle x position relative to ellipsecenter

-   -   y_(v)=P_(rel) _(x) ^(E)=vehicle y position relative to ellipse        center

The desired heading is then computed as:

$\begin{matrix}{\Psi_{D} = {{\tan^{- 1}\left( \frac{a^{2}x_{t}}{b^{2}y_{t}} \right)} - \pi}} & {{Eq}.\mspace{14mu} 29}\end{matrix}$

The horizontal acceleration command is formulated in the ellipse capturebearing reference frame. Hence a transformation matrix from the ellipsereference frame to the capture bearing reference frame (T_(E) ^(B)) iscomputed.

$\begin{matrix}{T_{E}^{B} = \begin{bmatrix}{\cos\left( \Psi_{D} \right)} & {- {\sin\left( \Psi_{D} \right)}} & 0 \\{\sin\left( \Psi_{D} \right)} & {\cos\left( \Psi_{D} \right)} & 0 \\0 & 0 & 1\end{bmatrix}} & {{Eq}.\mspace{14mu} 30}\end{matrix}$

The vehicle heading error relative to the ellipse capture bearing iscomputed as:ΔΨ=Ψ_(D)−Ψ_(t)+Ψ_(E)  Eq. 31

-   -   where Ψ_(t)=vehicle ground track angle        -   Ψ_(E)=ellipse heading relative to north

The position error relative to the ellipse tangent point is computed inthe capture bearing reference frame.

$\begin{matrix}{{\Delta\;{\overset{\rightharpoonup}{P}}^{B}} = {T_{E}^{B}\begin{Bmatrix}{P_{{rel}_{x}}^{E} - x_{t}} \\{P_{{rel}_{y}}^{E} - y_{t}} \\P_{{rel}_{z}}^{E}\end{Bmatrix}}} & {{Eq}.\mspace{14mu} 32}\end{matrix}$

The horizontal acceleration command is computed using the biased pursuitguidance law:a _(c) _(k) =−k _(p) ΔP ^(B) _(x) +k _(v) |{right arrow over (V)}_(I)|ΔΨ  Eq. 33

The total local vertical acceleration command vector is computed asfollows:

$\begin{matrix}{{\overset{\rightharpoonup}{a}}_{c}^{LV} = {{\left\lbrack T_{LV}^{E} \right\rbrack^{T}\left\lbrack T_{E}^{B} \right\rbrack}^{T}\begin{Bmatrix}a_{c_{h}} \\0 \\{{k_{p}\Delta\; P_{z}^{B}} - {k_{v}V_{I_{z}}} + {g} + {k_{p}k_{{FF}_{2,1}}V_{c}}}\end{Bmatrix}}} & {{Eq}.\mspace{14mu} 34}\end{matrix}$

where V_(c)=Airspeed command

-   -   |g|=9.81

This acceleration command vector is then processed through a translationfunction that generates native vehicle autopilot commands.

As has been alluded to, the present invention also accommodatesracetrack and figure-8 path orbit control. FIG. 19 is a schematicdiagram demonstrating various segments of the racetrack and figure-8patterns.

In one embodiment, the guidance laws used for racetrack orbit patternsare a combination of the waypoint guidance laws and the ellipse guidancelaws. The waypoint guidance law is used during the straight leg segmentsof the orbit patterns and the ellipse guidance law is used during theturn segments of the orbit patterns. The turn segments are constantradius; therefore the conic equations are simplified over that of theellipse.

In one aspect of the present invention, the description will now turn toan explanation of mathematical algorithms (step-by-step) for computing adesired vehicle location along the orbit pattern inertial path. Thisdesired location is illustratively an instantaneous point inthree-dimensional space that is used to formulate guidance errors. Theguidance algorithms for the racetrack and figure-8 patternsillustratively follow the same processing as the ellipse guidance lawwith slight computational variations that can be noted in thecalculations that follow. These calculations are based on the orbitpattern reference point and orbit pattern size and orientation selectedby the operator either graphically during real-time route editing orapriori during mission planning. The vehicle enters and exits an orbitpattern via an entrance path and an exit path, respectively. Theentrance path to an orbit pattern and the exit path from the orbitpattern are defined as follows: 1) The path from the waypoint preceedingan orbit pattern to the orbit pattern is defined as the tangent line tothe orbit pattern that passes through the waypoint (algorithmiccomputations defined below); and 2) The path from the orbit pattern tothe waypoint proceeding the orbit pattern is defined as the tangent lineto the orbit pattern that passes through the waypoint (algorithmiccomputations defined below). The orbit pattern desired locationcomputations are defined below. The coordinate frame definitions andtransformations were previously defined.

In accordance with one embodiment, the processing steps for orbitpattern desired location computations proceed as follows:

-   -   STEP ONE—Compute the ECEF position of the orbit pattern        reference point:        {right arrow over (P)} _(ref) ^(ECEF)=geo2ecef(λ,l,h)  Eq. 35        -   where {right arrow over (P)}_(ref) ^(ECEF)=ECEF position            vector of reference point            -   λ=Geodetic latitude of reference point            -   l=Geodetic longitude of reference point            -   h=Ellipsoidal altitude of reference point        -   NOTE: “geo2ecef” represents the coordinate transformation            defined herein within the Section entitled “Coordinate Frame            Definitions”    -   STEP TWO—Compute the ECEF position of the orbit pattern centroid        using the local vertical offset vector (the vertical component        of this offset vector is zero).        {right arrow over (P)} _(C) ^(ECEF) ={right arrow over (P)}        _(ref) ^(ECEF) +[R _(ECEF) ^(LV)]^(T) {right arrow over (P)}        _(offset)  Eq. 36        -   where T_(ECEF) ^(LV)=Local vertical to ECEF transformation            matrix            -   {right arrow over (P)}_(offset)=Local vertical offset                vector (vertical component is zero)    -   STEP THREE—The (x,y) coordinates of the orbit pattern relative        to the orbit pattern centroid at the current angle, t, in the        orbit pattern reference frame are computed as follows (the        z-component of the vector is zero; a is the orbit pattern        semi-major axis length and b is the orbit pattern semi-minor        axis lentgh):

$\begin{matrix}{{{\Delta\; P_{x}^{ELL}} = {b\;{\sin\left( t_{i} \right)}}}{{\Delta\; P_{y}^{ELL}} = \left\{ {{\begin{matrix}{a\;{\cos\left( t_{i} \right)}} & {ellipse} \\{a - {b\left( {1 - {\cos\left( t_{i} \right)}} \right)}} & \begin{Bmatrix}{{{racetrack}\&} -} \\{\frac{\pi}{2} \leq t \leq \frac{\pi}{2}}\end{Bmatrix} \\{{- a} + {b\left( {1 - {\cos\left( t_{i} \right)}} \right)}} & {otherwise}\end{matrix}{where}\zeta} = {\cos^{- 1}\left( \frac{b}{a - b} \right)}} \right.}} & {{Eq}.\mspace{14mu} 37}\end{matrix}$

-   -   STEP FOUR—Rotate the orbit pattern coordinate into the ECEF        reference frame:

$\begin{matrix}{{{\overset{\rightharpoonup}{P}}^{ECEF} = {{\overset{\_}{P}}_{c}^{ECEF} + {\left\lbrack T_{ECEF}^{E} \right\rbrack^{T}\Delta\;{\overset{\rightharpoonup}{P}}^{ELL}}}}{where}{{\overset{\rightharpoonup}{P}}^{ELL} = {{{\begin{bmatrix}{\Delta\; P_{x}^{ELL}} \\{\Delta\; P_{y}^{ELL}} \\0\end{bmatrix}\left\lbrack T_{ECEF}^{E} \right\rbrack}\,^{T}} = {{Transpose}\mspace{14mu}{of}\mspace{14mu}{ECEF}{\mspace{11mu}\;}{to}\mspace{14mu}{ellipse}}}}\mspace{14mu}{{coordinate}\mspace{14mu}{transformation}\mspace{14mu}{matrix}}} & {{Eq}.\mspace{14mu} 38}\end{matrix}$

-   -   STEP FIVE—Compute the latitude and longitude of the orbit        pattern coordinate:        (λ_(i) ,l _(i) ,h _(i))=ecef2geo({right arrow over (P)}        ^(ECEF))  Eq. 39        -   NOTE: “ecef2geo” represents the inverse of the “geo2ecef”            coordinate transformation defined herein within the Section            entitled “Coordinate Frame Definitions”    -   STEP SIX—Pass the computed parameters to the guidance law for        computation of the autopilot command inputs (e.g., utilizing the        algorithms were defined in the preceeding sections).

The UAV enters a racetrack orbit pattern along a capture path thatpasses tangent to the orbit pattern. This is the desired capture pathdue to the fact that the horizontal acceleration command at the point ofthe capture will be effectively zero, indicating that the vehicle doesnot require a correction to establish the orbit course at the time ofcapture.

In accordance with one embodiment, the processing steps for waypoint toorbit pattern segment calculation proceed as follows (the followingalgorithm applies to both the preceeding and proceeding waypoint paths):

-   -   STEP ONE—Using the ECEF location of the orbit pattern centroid        computed in steps 1 and 2 of the orbit pattern desired location        computation algorithm compute the position of the waypoint        (either preceeding or proceeding the orbit pattern, whichever        the case may be) relative to the orbit pattern centroid in the        ellipse reference frame as follows:        Δ{right arrow over (P)}_(v) ^(ELL) =T _(ECEF) ^(E)({right arrow        over (P)} _(w) ^(ECEF) −{right arrow over (P)} _(c)        ^(ECEF))  Eq. 40    -   where Δ{right arrow over (P)}_(v) ^(ELL)=waypoint position        relative to orbit pattern center in ellipse reference frame        -   {right arrow over (P)}_(w) ^(ECEF)=waypoint ECEF position        -   {right arrow over (P)}_(c) ^(ECEF)=orbit pattern centroid            ECEF position        -   T_(ECEF) ^(E)=ECEF to ellipse reference frame coordinate            transformation matrix    -   STEP TWO—Compute the orbit pattern tangent point which lies on        the line passing through the waypoint:

$\begin{matrix}{x_{t} = \left\{ {{\begin{matrix}{{- k}\frac{b\sqrt{y_{v}^{2} - a^{2}}}{y_{v}}} & {x_{v} = 0} \\{- \frac{b^{2}\left( {{- 1} + {\frac{1}{2}\frac{y_{v}\begin{pmatrix}{{2b^{2}y_{v}} +} \\{2k\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {x_{v}^{2}b^{2}y_{v}^{2}x_{v}^{2}}}}\end{pmatrix}}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}}} \right)}{x_{v}}} & {x_{v} > 0} \\{- \frac{b^{2}\left( {{- 1} + {\frac{1}{2}\frac{y_{v}\begin{pmatrix}{{2b^{2}y_{v}} -} \\{2k\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}\end{pmatrix}}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}}} \right)}{x_{v}}} & {x_{v} < 0}\end{matrix}y_{t}} = \left\{ {{\begin{matrix}\frac{a^{2}}{y_{v}} & {x_{v} = 0} \\{{\frac{1}{2}\frac{\begin{pmatrix}{{2b^{2}y_{v}} +} \\{2k\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}\end{pmatrix}a^{2}}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}} + {kd}} & {x_{v} > 0} \\{{\frac{1}{2}\frac{\begin{pmatrix}{{2b^{2}y_{v}} -} \\{2k\sqrt{{a^{2}x_{v}^{4}} - {a^{2}x_{v}^{2}b^{2}} + {b^{2}y_{v}^{2}x_{v}^{2}}}}\end{pmatrix}a^{2}}{{a^{2}x_{v}^{2}} + {b^{2}y_{v}^{2}}}} - {kd}} & {x_{v} < 0}\end{matrix}{where}b} = {{{semi}\text{-}{minor}\mspace{14mu}{{axis}\left( {{half}\mspace{14mu}{orbit}{\mspace{11mu}\;}{region}{\mspace{11mu}\;}{box}\mspace{14mu}{width}} \right)}a} = \left\{ {{\begin{matrix}\begin{matrix}{{semi}\text{-}{major}\mspace{14mu}{axis}} \\\left( {{half}\mspace{14mu}{orbit}{\mspace{11mu}\;}{region}{\mspace{11mu}\;}{box}\mspace{14mu}{length}} \right)\end{matrix} & {ellipse} \\b & {racetrack}\end{matrix}d} = {{\begin{pmatrix}{{half}\mspace{14mu}{orbit}{\mspace{11mu}\;}{region}} \\{{box}\mspace{14mu}{length}}\end{pmatrix} - {\begin{pmatrix}{{half}\mspace{14mu}{orbit}{\mspace{11mu}\;}{region}} \\{{box}\mspace{14mu}{width}}\end{pmatrix}k}} = \left\{ {{\begin{matrix}1 & {{for}\mspace{14mu}{preceeding}\mspace{14mu}{waypoint}} \\{- 1} & {{for}{\mspace{11mu}\;}{proceeding}\mspace{14mu}{waypoint}}\end{matrix}x_{v}} = {{\Delta\;{{\overset{\rightharpoonup}{P}}_{v}^{ELL}(x)}y_{v}} = \left\{ \begin{matrix}{\Delta\;{{\overset{\rightharpoonup}{P}}_{v}^{ELL}(y)}} & \begin{matrix}{{ellipse}\mspace{14mu}{or}} \\{x_{v} = 0}\end{matrix} \\{{\Delta\;{{\overset{\rightharpoonup}{P}}_{v}^{ELL}(y)}} - {kd}} & \begin{matrix}{\left\{ {racetrack} \right\}\mspace{14mu}} \\{{{and}\mspace{14mu} x_{v}} > 0}\end{matrix} \\{{\Delta\;{{\overset{\rightharpoonup}{P}}_{v}^{ELL}(y)}} + {kd}} & \begin{matrix}{\left\{ {racetrack} \right\}\mspace{14mu}} \\{{{and}\mspace{14mu} x_{v}} < 0}\end{matrix}\end{matrix} \right.}} \right.}} \right.}} \right.} \right.} & {{Eq}.\mspace{14mu} 41}\end{matrix}$

-   -   STEP THREE—Rotate the orbit pattern tangent point into the ECEF        reference frame:

$\begin{matrix}{{{\overset{\rightharpoonup}{P}}_{t}^{ECEF} = {{\overset{\_}{P}}_{c}^{ECEF} + {\left\lbrack T_{ECEF}^{E} \right\rbrack^{T}\Delta\;{\overset{\rightharpoonup}{P}}_{t}^{ELL}}}}{where}{{\Delta\;{\overset{\rightharpoonup}{P}}^{ELL}} = {{{\begin{bmatrix}x_{t} \\y_{t} \\0\end{bmatrix}\left\lbrack T_{ECEF}^{E} \right\rbrack}\,^{T}} = {{Transpose}\mspace{14mu}{of}\mspace{14mu}{ECEF}{\mspace{11mu}\;}{to}\mspace{14mu}{ellipse}\mspace{14mu}{coordinate}\mspace{14mu}{transformation}\mspace{14mu}{matrix}}}}} & {{Eq}.\mspace{14mu} 42}\end{matrix}$

-   -   STEP FOUR—Compute the latitude and longitude of the orbit        pattern tangent point:        (λ_(t) ,l _(t) ,h _(t))=ecef2geo({right arrow over (P)} _(t)        ^(ECEF))  Eq. 43    -   STEP FIVE—Insert a waypoint leg connecting the waypoint and the        computed orbit pattern tangent point

FIG. 20 is a schematic diagram demonstrating an example of a programmedroute using the defined loiter algorithms. Within FIG. 20, items 4, 7,and 9 represent orbit patterns and the remaining numbered elementsrepresent waypoints. In accordance with one embodiment, the orbitguidance laws are configured to allow the operator to input either adesired orbit time or a desired number of orbit laps. The UAV will exitthe orbit pattern when either the specified orbit time or specifiednumber of orbit laps has been completed.

An interesting characteristic of the loiter pattern embodiments of thepresent invention is that one is able to mathematically define a desiredlocation on a path in association with a given point in time. Points canbe defined relative to a center point, even relative to a moving centerpoint.

C. Remote Directional Command Mode

In accordance with one aspect of the present invention, as is inferredby block 140 in FIG. 1, a remote directional command (RDC) control modeis implemented. The versatility of the overall control system design ofthe described VACS architecture makes implementation of an RDC controlmode relatively straightforward.

Inertial turn rates are kinematically related to acceleration throughmultiplication of the inertial velocity magnitude (a=Vω). Hence, in thehorizontal channel, an acceleration command can be generated for theautopilot by multiplying a desired or commanded turn rate by theinertial velocity magnitude. To accomplish this guidance law, theoperator's horizontal control stick input is linearly mapped to ahorizontal turn rate command in which the maximum stick position isequal to the maximum allowable horizontal turn rate.

The vertical channel manual control mode is a little different. For mostUAV applications the vertical stick position will translate into aclimb/descent rate command. It is more intuitive for operators tocontrol the vertical channel via climb rate. Hence, in accordance withone embodiment, a look-up table of climb performance as a function ofvehicle state (altitude and airspeed) is incorporated into thealgorithms (the table is illustratively programmable to accommodatemultiple UAV platforms). On each pass through the guidance software, themaximum climb rate is computed. The vertical control stick location isthen linearly mapped to this maximum climb rate (center stick=zero climbrate, max stick=max climb rate). This climb rate command is then used tocompute a flight path angle (gamma) command, which is fed into a gammacontrol guidance law (defined later in this section). A combination ofcontrol input device rate limiting and guidance command rate limitingillustratively results in a robust design that prevents the operatorfrom being able to overdrive, stall, spin or in any other way crash thevehicle.

It should be noted that practically any known commercial control inputdevice can be utilized for RDC control without departing from the scopeof the present invention. For example, a USB game pad can be utilizedthereby providing relative compactness and versatility. In accordancewith one embodiment, the game pad utilized has a throttle slide control,a plurality of control buttons, and two thumb control sticks—one ofwhich is used to steer the UAV and the other used to steer the UAVimaging sensor.

In accordance with one aspect of the present invention, the controlsystem software translates the vehicle control stick motion as follows:

-   -   1. Forward (away from the operator)—descent rate command    -   2. Backward (toward the operator)—climb rate command    -   3. Left—left turn rate command    -   4. Right—right turn rate command        The raw stick position readings are illustratively calibrated        and normalized to range from −1.0 to 1.0 in both channels where        (0,0) represents the center (neutral) stick position. When the        stick is in the neutral position (0,0), the vehicle flies a        straight and level profile. In accordance with one embodiment,        the off-board control system software (i.e., the software        resident on the ground station) maps the stick range limits as        follows:    -   1. Maximum horizontal stick position (±1)—max vehicle turn rate    -   2. Maximum forward stick position (+1)—max vehicle descent rate    -   3. Maximum aft stick position (−1)—max vehicle climb rate

In one aspect of the present invention, the vehicle max climb rate is afunction of altitude and airspeed. The off-board control softwareillustratively maintains a database of the vehicle max climb rate andinterpolates based on current flight conditions to obtain theinstantaneous control limit. This methodology will prevent the operatorfrom overdriving the vehicle. A similar methodology is used for descentrate, although the descent rate is not as restrictive as the climb rateand requires a more empirical approach to setting.

In accordance with one aspect of the present invention, the followingequations define the basic simplified manual control approach. Thealgorithm maintains a set of vertical and horizontal referenceconditions that are used to command the vehicle when the operator letsgo of the stick. First, the vertical stick position is checked formovement and the associated vertical commands and reference conditionsare computed:

$\begin{matrix}{\;{{{{{if}\mspace{14mu}{{\delta_{v_{i}} - \delta_{v_{i - 1}}}}} > ɛ}{H_{ref} = H}{R = 0}{else}{R_{i} = {R_{i - 1} + {V_{horz}\Delta\; t}}}{endif}{{\overset{.}{H}}_{c} = {\delta_{v_{i}}{\overset{.}{H}}_{\max}}}{\gamma_{c} = {\sin^{- 1}\left( \frac{{\overset{.}{H}}_{c}}{V_{I}} \right)}}{where}{\delta_{v} = {{vertical}\mspace{14mu}{control}\mspace{14mu}{stick}\mspace{14mu}{position}}}\text{}\;{ɛ = {{control}\mspace{14mu}{stick}\mspace{14mu}{measurement}}}{\mspace{11mu}\;}\;{noise}\text{/}{freeplay}\mspace{14mu}{tolerance}}{H_{ref} = {{reference}\mspace{14mu}{altitude}}}{H = {{vehicle}\mspace{14mu}{altitude}}}\text{}{R = {{integrated}\mspace{14mu}{path}\mspace{14mu}{length}}}\mspace{14mu}\;{{during}\mspace{14mu}{vertical}\mspace{14mu}{maneuver}}{{\overset{.}{H}}_{c} = {{climb}\text{/}{descent}\mspace{14mu}{rate}\mspace{14mu}{command}}}{\overset{.}{H} = {{vehicle}\mspace{14mu}{altitude}\mspace{14mu}{rate}}}{\gamma_{c} = {{flight}\mspace{14mu}{path}\mspace{14mu}{angle}{\mspace{11mu}\;}{command}}}{V_{I} = {{vehicle}\mspace{14mu}{inertial}\mspace{14mu}{velocity}\mspace{14mu}{magnitude}}}}} & {{Eq}.\mspace{14mu} 44}\end{matrix}$Next, the horizontal stick is checked for movement and the associatedhorizontal commands and reference conditions are computed:

$\begin{matrix}{{{{if}\mspace{14mu}{\delta_{h}}} > ɛ}{{\overset{.}{\Psi}}_{c} = {\delta_{h}{\overset{.}{\Psi}}_{\max}}}{\Psi_{ref} = \Psi_{t}}{{\overset{\rightharpoonup}{P}}_{ref}^{LV} = \left\{ {0,0} \right\}^{T}}{else}{{\overset{\rightharpoonup}{P}}_{{ref}_{\mspace{11mu} i}}^{LV} = {{\overset{\rightharpoonup}{P}}_{{ref}_{\mspace{14mu}{i - 1}}}^{LV} + {{\overset{\rightharpoonup}{V}}_{h}\Delta\; t}}}{{\overset{\rightharpoonup}{P}}_{ref}^{W} = {T_{LV}^{W}{\overset{\rightharpoonup}{P}}_{ref}^{LV}}}{endif}{where}{\delta_{h} = {{horizontal}\mspace{14mu}{control}\mspace{14mu}{stick}\mspace{14mu}{position}}}{{\overset{.}{\Psi}}_{c} = {{horizontal}\mspace{14mu}{turn}\mspace{14mu}{rate}\mspace{14mu}{command}}}{\overset{.}{\Psi} = {{horizontal}\mspace{14mu}{turn}\mspace{14mu}{rate}}}{\Psi_{ref} = {{reference}\mspace{14mu}{heading}}}{\Psi_{t} = {{vehicle}\mspace{14mu}{ground}\mspace{14mu}{track}\mspace{14mu}{angle}}}{{\overset{\rightharpoonup}{P}}_{ref} = {{reference}\mspace{14mu}{position}}}} & {{Eq}.\mspace{14mu} 45}\end{matrix}$

The above equations illustrate how trajectory synthesis is employed toguide the vehicle on a straight and level path when the control stick isreturned to zero. This synthesis technique generates an inertial path towhich the vehicle guides, thus ensuring that inertial sensor errors donot cause the vehicle to deviate from the operator's expected course.

The airspeed command is computed based on the slide control setting:V _(c) =V _(min)+δ_(t)(V _(max) −V _(min))  Eq. 46where δ_(t)=slide control setting

Any of a variety of vertical channel control schemes can be implementedwithout departing from the scope of the present invention, includingboth position and velocity reference control laws. It is intuitivelyobvious that when the operator commands a climb or descent via themanual control operation, the only altitude of concern is the altitudeat which to level off. Hence, the actual implementation of the controllaw does not require a position-slave component. This reduces the orderof the control law to a first order control law in which the velocitycommand term is acted upon to generate an acceleration command to theautopilot. In accordance with one embodiment, the followingperturbational first-order control law is illustratively used for thealtitude rate control:

$\begin{matrix}{a_{c_{up}} = {{\frac{V_{I}}{\tau}\left( {\gamma - \gamma_{c}} \right)} - g}} & {{Eq}.\mspace{14mu} 47}\end{matrix}$

-   where-   a_(c) _(up) =local vertical UP acceleraion command-   γ=flight path angle-   γ_(c)=flight path angle command=

$\sin^{- 1}\left( \frac{{\overset{.}{h}}_{c}}{V} \right)$

-   {dot over (h)}_(c)=altitude rate command-   τ=guidance law time constant-   g=acceleration of gravity-   |V_(I)|=inertial velocity magnitude

In one embodiment, the time constant is a tunable parameter that can beadjusted for specific platforms. For example, the time constant used fora given vehicle might be 0.3 seconds, whereas the time constant used foranother vehicle might be 0.1 seconds. The vertical channel guidancegenerally works in coordination with the automatic speed control loop.In other words, simply commanding a constant throttle setting as opposedto a constant speed setting can easily drive the vehicle into a stallcondition when maximum (or near maximum) climb rates are commanded. Byincluding the automatic speed control design and mapping the operator's“throttle” control input to a speed command as opposed to a throttlesetting the problem is alleviated.

In accordance with one embodiment, the horizontal acceleration commandis computed as

$\begin{matrix}{a_{c_{h}} = \left\{ \begin{matrix}{{{- k_{p}}{{\overset{\rightharpoonup}{P}}_{ref}^{w}({across})}} - {k_{v}{V_{horz}}\left( {\Psi_{t} - \Psi_{ref}} \right)}} & {{\delta_{h}} \leq ɛ} \\{V_{I}{\overset{.}{\Psi}}_{c}} & {{\delta_{h}} > ɛ}\end{matrix} \right.} & {{Eq}.\mspace{14mu} 48}\end{matrix}$

It should be noted that when the horizontal stick is in the neutrallocation a biased pursuit guidance law is used to maintain a constantheading. The local vertical acceleration command vector is thenillustratively computed as:

$\begin{matrix}{{\overset{\rightharpoonup}{a}}_{c}^{LV} = {\begin{Bmatrix}{a_{c_{h}}{\cos\left( \Psi_{t} \right)}} \\{{- a_{c_{h}}}{\sin\left( \Psi_{t} \right)}} \\a_{c_{UP}}\end{Bmatrix}.}} & {{Eq}.\mspace{14mu} 49}\end{matrix}$

This acceleration command vector is then illustratively processedthrough a translation layer and delivered to the autopilot system.

An additional aspect of the present invention pertains to control stickcommand rate limiting. A key desired objective of the simplified manualcontrol modes described herein is that the control modes will resist theoperator's ability to overdrive the vehicle. In accordance with oneembodiment, a robust, algorithmic approach to aid in the achievement ofthis objective is to implement a rate limit on the operator's controlstick command inputs. A simple rate-limiting algorithm has a dynamiceffect similar to passing the commands through a low-pass filter. Therate limiting essentially attenuates high frequency command inputs. Thebenefit to the controller is that rate limiting the command inputsenables an elimination of high frequency “jerks” from the command stick.Further an avoidance is enabled of inadvertent and unnecessarily largesteps and high frequency impulses directed to the controller. This, inturn, minimizes the transient effects of the closed-loop on the humanoperator's perception of the vehicle response to his/her commands. Inother words, with the control stick rate limiting algorithm functioning,the operator always sees the vehicle respond smoothly to the directionalcommands that he/she is supplying. In accordance with one embodiment,the control stick rate limiting is a tunable parameter within VACS andcan be adjusted to satisfy the specific performance desires of a givenoperator with a given vehicle under VACS control.

Another aspect of the present invention pertains to an automatic speedcontrol loop. Important to the application of a robust simplified manualcontrol capability is the ability of the embedded controller to maintainspeed, even through harsh maneuvering environments. Consider a scenariowherein an operator commands a hard turn, a max climb, or a combinedclimb and turn maneuver, the VACS controller will rapidly orient thevehicle into the desired maneuver (flight path and turn rate). Themaneuver, in turn, will require the vehicle to pull a largeangle-of-attack, which results in increased drag, or to fly a glideslope in which the effects of gravity in the axial channel aresignificant enough to induce a rapid deceleration. To expect theoperator to keep up this rapidly changing dynamic environment bymanually adjusting the throttle would directly oppose the goal of thesimplified manual control design. Hence, in accordance with oneembodiment of the present invention, an automatic speed control loop iscoupled into the system. A basic implementation allows the operator toenter a preprogrammed speed setting (cruise for best range, cruise forbest endurance, cruise at max speed, etc) or a manual speed settingusing a typical joystick throttle input. For the manual speed setting,the control stick throttle setting is not mapped to throttle setting,but rather mapped to a speed command that is linearly proportional tothe control setting. In other words, the minimum control setting maps tothe vehicle minimum control speed and the maximum control setting mapsto the vehicle maximum cruise speed. The remaining settings are mappedlinearly between the min and max speeds.

As the vehicle decelerates through commanded maneuvers, the automaticspeed loop responds and adjusts the throttle setting to maintain thedesired speed programmed by the operator. Even as the operator adjustshis manual speed control, the flight software is simply adjusting thespeed command to the autospeed loop, which is always running. Theadvantage is that the bandwidth of the control system is higher than thebandwidth of a human operator; hence, using VACS, the operator generallycannot command a maneuver that ultimately drives the vehicle tostall—the flight computer is continuously adjusting the throttle tomaintain the proper speed setting.

Another aspect of the present invention pertains to climb gradientlimiting. When mapping the vertical control stick command to a climbrate command, the vehicle climb rate performance capability isillustratively taken into account. The maximum climb rate of the vehicledirectly corresponds to the maximum vertical control stick deflection.When a combined climb and turn maneuver is commanded, the net reductionin climb rate capability resulting from the out-of-plane accelerationcomponent required to generate the turn rate is accounted for. There isa closed form analytic climb rate reduction that can be computed toaccount for the turn. In accordance with one embodiment, this reductionin climb rate is computed as:

$\begin{matrix}{{\Delta\overset{.}{h}} = {- \frac{2\frac{\partial C_{D}}{\partial\left( C_{L}^{2} \right)}m^{2}{\overset{.}{\Psi}}^{2}V}{\rho\;{gS}_{ref}}}} & {{Eq}.\mspace{14mu} 50}\end{matrix}$

-   where

$\frac{\partial C_{D}}{\partial\left( C_{L}^{2} \right)} = {{vehicle}\mspace{14mu}{drag}\mspace{14mu}{polar}\mspace{14mu}{{constant}(k)}}$

-   m=vehicle mass-   {dot over (Ψ)}=turn rate command-   V=inertial velocity-   ρ=air density-   g=acceleration of gravity-   S_(ref)=aerodynamic reference area

The maximum climb rate used to generate the flight path referencecommand during the manual control mode is reduced by the amount computedusing the above equation. The combination of this reduction, along withthe limiting algorithms and speed control loop discussed in thepreceding sections offers a robust manual control system design thatprevents the operator from overdriving the UAV.

D. Line-of-Sight Slave Control Mode

In accordance with one aspect of the present invention, as is indicatedby block 136 in FIG. 1, a line-of-sight (LOS) slave control mode isimplemented. The versatility of the overall control system design of thedescribed VACS architecture makes implementation of this control moderelatively straightforward.

The underlying operational concept of the LOS slave control mode isillustratively defined by the fact that the operator is ultimatelyinterested in the imagery captured and transmitted by the UAV. The goalof the guidance mode therefore becomes to offer the operator thecapability to manually slew the UAV sensor while surveying a battlefieldor other topological region with complete disregard for the aviation ordirection of the UAV. To accomplish this guidance objective, the vehicleis slaved to the sensor line-of-sight. To maximize the operator'sprobability of visual object recognition, the guidance policy is toalign the heading of the UAV to the horizontal sensor line-of-sight.With this policy, the vehicle is always commanding a path toward thedesired surveillance area. A simple pursuit guidance law is employed toachieve the stated guidance goal.

In accordance with one embodiment of LOS slave control, the applicableguidance law commands the nose of the UAV to align with centerline ofthe gimbaled sensor by issuing the following horizontal accelerationcommand:

$\begin{matrix}{a_{c_{h}} = \left\{ \begin{matrix}{{{- k_{p}}{{\overset{\rightharpoonup}{P}}_{ref}^{W}({across})}} - {k_{v}{V_{horz}}\left( {\Psi_{t} - \Psi_{ref}} \right)}} & {{\delta_{h}} \leq ɛ} \\{{- K_{V}}{V_{t}}{\Delta\Psi}} & {{\delta_{h}} > ɛ}\end{matrix} \right.} & {{Eq}.\mspace{14mu} 51}\end{matrix}$ΔΨ represents the angle between the vehicle centerline and the sensorhorizontal line-of-sight angle. The sensor horizontal line-of-sightangle is derived from the platform gimbal angles.

Generally speaking, the directional-response autopilot, combined withthe stabilized platform, allows a single minimally trained operator toeasily conduct a UAV surveillance mission. A further level of usersimplification is achieved by combining seeker designation command logicwith the outer loop guidance. This mixing provides Line-of-Sight Slavemode capability in which the operator's point of reference is the imagescene transmitted from the UAV's on-board camera. In this mode theoperator does not provide direction commands to the UAV. Instead, theoperator focuses his attention on the tactical situation display,commanding the look angle of the UAV's on-board sensor to survey thebattlefield (or other topographical region for non-militaryapplications) while the UAV autonomously commands a flight profile whichis slaved to the operator's sensor line-of-sight commands. Thisintegration of the camera platform with the guidance provides thefollowing benefits:

-   -   1. Time-on-station loiter control which can be easily selected        and designated.    -   2. Further reduction of workload on the operator, who can now        focus primarily on the surveillance aspects of the mission.    -   3. An easily adaptable relative Navigation method.

FIG. 21 is a diagrammatic illustration demonstrating how LOS slavecontrol is implemented with the ground station display in accordancewith one aspect of the present invention. The display is illustrativelya top-view with a schematic of the aircraft for easierconceptualization. The outer circle around the aircraft isillustratively a projection of the entire field-of-view onto the ground.The smaller pie-shaped queue is illustratively a ground projection ofthe current seeker borsight position. These are calculated by the groundstation software from the positional information and seeker angle sentacross the data-link. The remote operator can illustratively opt toeither keep the cursor active as the continual steering point, or he/shecan designate a “surveillance-point” by clicking on a desired groundlocation. In the latter case, the staring point would be captured so thecursor could be moved to a new constant location.

If the pilot chooses a surveillance location outside the total FOV, thenthe outer loop guidance will illustratively follow a command-to-LOS modeguide law until the UAV flight path points toward the target. Once thedesired staring-point comes within a minimum range threshold, theguidance automatically trips into a loiter pattern (eitherconstant-radius or elliptical) to maintain a station with a singlekey-click while he/she conducts other activities. FIGS. 22A & 22Btogether demonstrate the surveillance-point approach scenario.

If a constant location is selected within the minimum turning radius,then the guidance will fly over the surveillance-point and plan anout-and-back pattern to avoid a singularity in the loiter guide-law.This can be easily achieved by inserting waypoint legs autonomously. Ifthe operator chooses, he/she can select a standoff range (or accept thedefault range) for surveillance over a hostile target. The line-of-sightcommands will also comprehend the offset location to track on thedesired location. This is achieved by inserting the offset range vectorin the positional component of the loiter guide-law.

The following simplified equations are used to show the basic structureof the LOS Slave mode guidance:

$\begin{matrix}{\;{{{If}\mspace{14mu}\left( {R_{Target} > {Loiter\_ Threshhold}} \right)\mspace{14mu}{then}}{{\overset{.}{\psi}}_{Cmd} = {K_{\overset{.}{\psi}}\left( {\lambda_{Horiz} - \psi_{Heading}} \right)}}{{\overset{.}{\gamma}}_{Cmd} = {{K_{H}\left( {H_{CMD} - H} \right)} + {H_{\overset{.}{H}}\overset{.}{H}} + \frac{g}{V}}}{else}{{\overset{.}{\psi}}_{Cmd} = {{K_{\psi}{\Delta\Psi}} + {K_{p}\left( {{P_{Turn} - {{{{\overset{\_}{R}}_{Target} + {\overset{\_}{R}}_{{Stand} - {Off}}}}{\overset{.}{\gamma}}_{Cmd}}} = {{{K_{H}\left( {H_{CMD} - H} \right)} + {K_{\overset{.}{H}}\overset{.}{H}} + {\frac{g}{v}{endif}{where}R_{Target}}} = {{{Horizontal}{\mspace{11mu}\;}{Range}\text{-}{to}\text{-}{Target}{\overset{.}{\psi}}_{Cmd}} = {{{Horizontal}{\mspace{11mu}\;}{Turning}\mspace{14mu}{Rate}\mspace{14mu}{Command}{\Delta\Psi}} = {{{Heading}\mspace{14mu}{Error}\mspace{14mu}{Relative}\mspace{14mu}{To}\mspace{14mu}{Loiter}\mspace{14mu}{Path}\lambda_{Horiz}} = {{{Horizontal}\mspace{14mu}{Line}\text{-}{of}\text{-}{Sight}{\mspace{11mu}\;}{to}\mspace{14mu}{Target}{\overset{.}{\gamma}}_{Cmd}} = {{{Vertical}\mspace{14mu}{Turning}\mspace{14mu}{Rate}\mspace{14mu}{Command}\Psi_{Heading}} = {{{Heading}\mspace{14mu}{Angle}P_{Turn}} = {{{Loiter}\mspace{14mu}{Turning}\mspace{14mu}{Radius}H} = {Altitude}}}}}}}}}}\mspace{20mu} \right.}}}}} & {{Eq}.\mspace{14mu} 52} \\{g = {{Gravity}\mspace{14mu}{Acceleration}\mspace{14mu}{Magnitude}}} & \; \\{V = {{Vehicle}\mspace{14mu}{Inertial}\mspace{14mu}{Velocity}\mspace{14mu}{Magnitude}}} & \;\end{matrix}$

The above equations show two active horizontal guidance terms whenflying the constant turning radius circle. The first term is the dampingterm which drives the vehicle to align its ground track with the desiredcircular loiter pattern and is the dominating term. The second term is apositional term to help maintain the constant arc.

In accordance with one aspect of the present invention, sensor-slavemode commands are generated by an autonomous line-of-sight drivenfunction, in which the command objectives are generated by thenecessities of the function rather than by an operator. For example, afunction designed to command a raster-scan of a particular surveillancearea, or a function designed to scan a long a roadway could be used togenerate sensor slave commands. Another example is a function designedto generate line-of-sight commands for UAV-to-UAV rendezvous formationflying.

E. Ground Collision Avoidance System (GCAS)

In accordance with one aspect of the present invention, as is indicatedby block 120 in the FIG. 1 architecture, a ground collision avoidancesystem (GCAS) provides an automated mechanism enabling the controlsystem to avoid terrain without having to task the operator withstudying altitude above ground for each vehicle under his or hercontrol. In accordance with one embodiment, the GCAS provides theoperator with some form of situational awareness information about anupcoming collision (e.g., a warning signal). If the user does not reactto that information, the GCAS will automatically avoid the terrain andlet the user know the system is in an auto-avoidance mode. During thismode, the user is illustratively locked out from making flight pathchanges until the system has cleared the offending terrain.

In accordance with one embodiment, the operator is provided with a timerdisplay that counts down a time period within which the operator canmanually avoid a high potential terrain collision. If the operator doesnot manually steer off of the collision path during the time period,then the GCAS will initiate the auto-avoidance mode.

In accordance with one embodiment, an altitude profile sensor is set upto provide data for GCAS purposes. While other known sensors can beutilized without departing from the scope of the present invention, onesuitable ground terrain sensor system is the Digital Terrain ElevationData (DTED) Level 1 database available from the National Imagery andMapping Agency (NIMA). The spacing for Level 1 DTED is approximately 93meters, which somewhat limits the amount of surface information the GCASalgorithm uses. However, the GCAS algorithm is illustratively genericand can accept Level 2 DTED for a higher resolution model. It should benoted that it is also within the scope of the present invention to adopteven more advanced terrain description mechanisms to provide terraintopology map information for the ground collision avoidance logic.

In accordance with one embodiment, a first input to the GCAS is adesired clearance height above terrain for a vehicle to be controlled.Once the desired clearance has been defined, the GCAS algorithm producesa terrain altitude profile. The profile is created from the DTED mapsusing a scan pattern that accounts for Navigation and DTED errors.

FIG. 23 is a schematic representation of a top view of a scan patternwithin the context of the GCAS. The scan pattern starts at the vehicleposition. A horizontal uncertainty box is generated. A maximum terrainaltitude is then calculated within the uncertainty box. The uncertaintybox is then propagated forward adjusting for heading and any otheruncertainty. The algorithm then determines the maximum altitude in thenew uncertainty boxes and continues forward an amount to occupy alimited fly-out time (e.g., a 60 second fly-out). The maximum values forthese uncertainty boxes are used to feed the terrain profile for theGCAS guidance.

The philosophy behind the design of the GCAS system is to take thecurrent vehicle position and fly out a medium fidelity simulation as ifthe operator had commanded a maximum g pull up. While the simulationperforms this pull up, the algorithm monitors vehicle altitude andground altitude and attempts to predict at what point the vehicle willintersect the terrain.

FIG. 24 is a schematic diagram demonstrating of a sample trajectory.Assuming the vehicle is flying with current velocity V_(o), thealgorithm starts at the current vehicle position and flies a maximum gpull up trajectory. The maximum g pull up is an acceleration commandgenerated according to the following equation:

$\begin{matrix}{a_{c} = \frac{{QSC}_{L_{\max}}}{m}} & {{Eq}.\mspace{14mu} 53}\end{matrix}$where

-   Q=dynamic pressure-   S=vehicle aerodynamic reference area-   C_(L) _(max) =vehicle maximum lift coefficient-   m=vehicle mass    The algorithm then assumes a constant initial velocity and projects    the trajectory along the velocity line to estimate a time to fly up.    The time to fly up represents the time to start the maneuver in    order to avoid the terrain by an amount equal to the minimum descent    altitude. The minimum descent altitude is a constant and represents    the minimum height above the terrain for the platform through the    terrain avoidance mode.

After the algorithm finds the minimum altitude above ground through thefly-out trajectory, the closure rate is computed based on the initialvelocity and the velocity at the minimum altitude above ground.

$\begin{matrix}{V_{c} = \frac{{V_{H,0}*V_{U,{MinAgl}}} - {V_{H,{MinAgl}}*V_{U,0}}}{{\overset{\rightharpoonup}{V}}_{MinAgl}}} & {{Eq}.\mspace{14mu} 54}\end{matrix}$

Once the closing rate has been computed, the value is limited (e.g.,limited to 2 feet/second) to avoid division by zero problems in the timeto fly up calculation.V _(c)=max(V _(c),2.0)  Eq. 55

Once the closure rate computation is complete, the time to fly up iscalculated as:

$\begin{matrix}{{TTFU} = \frac{\left( {H_{MinAgl} - {MDA}} \right)}{V_{c}}} & {{Eq}.\mspace{14mu} 56}\end{matrix}$

The MDA variable represents the minimum descent altitude, or the minimumaltitude the vehicle should attain during the climb out. in accordancewith one embodiment, the time to fly up is computed periodically (e.g.,every 1 Hz) and reported to the operator station (i.e., the groundcontrol station). Should the time to fly up reduce to zero, the guidancecode will perform the maximum g pull up maneuver while ignoring anycommands from the operator station. Once the fly out is complete and thetime to fly up returns to a predetermined threshold (e.g., greater than10 seconds), control is relinquished and returned to the operatorstation.

In accordance with one embodiment, in order to perform the simulation infaster than real time, the high fidelity simulation is updated forcomputational simplicity. Accordingly, the design flies a paired downversion of the vehicle simulation in a faster than real-time environmentto estimate when the vehicle might impact the ground. For example, thebaseline simulation can be adapted with the following changes:

-   -   Truth Navigation model    -   Truth actuator models    -   No wind model    -   Reduced simulation time step to 16 Hz

These are examples of changes that can be made to enable performance ofa flyout simulation of the vehicle in a faster than real-timeenvironment.

In accordance with one embodiment, the simulation has the capability tofly out 10 seconds of medium fidelity data and then extrapolate foranother 50 seconds of data giving a 1 minute window of simulated data.The data provides time for the max g-pull up maneuver to execute andacquire the desired flight path angle. Once that flight path angle iscaptured, an inertial propagation for the next 50 seconds provides anaccurate assessment of the vehicle motion.

In accordance with one embodiment, the operator station (e.g., theground control station including the operator interface) is configuredto provide the operator with an opportunity to understand that thevehicle is about to go into a GCAS maneuver. For example, the time tofly up variable from the GCAS simulation is transmitted to the operatorstation. If the time to fly up value reduces to a value less than orequal to a predetermined value (e.g., 10 seconds), an indicator isprovided to the operator (e.g., the vehicle on the display turns yellow)and a counter is added to show the estimated time to fly up. Should thatnumber reduce to zero, an indication is provided (e.g., the vehicleturns red) showing that the operator no longer has control of thevehicle and the ground collision avoidance maneuver is currently beingexecuted.

IX. Translator

As was described in relation to FIG. 5, a translation layer can beimplemented to translate guidance commands into reference commandsappropriate for the specific autopilot implementation.

In accordance with one embodiment, an exemplary translation layerimplementation will now be provided. After the guidance algorithmsexecute, the outputs are translated to the native vehicle autopilotcommands. The equations below provide example kinematic translationsfrom the guidance acceleration commands to native vehicle autopilotcommands. These equations demonstrate the principal that vehicle motionis activated through acceleration. The methods that various vehiclesemploy to generate acceleration are numerous (bank angle autopilot,acceleration autopilot, heading control autopilot, altitude controlautopilot, etc). Since the control algorithms described herein generateacceleration commands that can be kinematically translated into any ofthese native autopilot commands, the guidance algorithms truly provide ageneralized library of control laws that can control any vehicle throughthat vehicle's native atomic functions. Ubiquitous acceleration controltechniques enable VACS to synthesize control commands for any vehicle,including air, ground, or sea-based.

$\begin{matrix}{{{a_{v} = {{vertical}{\mspace{11mu}\;}{plane}\mspace{14mu}{acceleration}\mspace{14mu}{command}}}{a_{h} = {{horizontal}{\mspace{11mu}\;}{plane}\mspace{14mu}{acceleration}\mspace{14mu}{command}}}{\phi = {{\tan^{- 1}\left( \frac{a_{h}}{a_{v}} \right)} = {{bank}\mspace{14mu}{angle}{\mspace{11mu}\;}{command}}}}{a_{T} = {\sqrt{a_{v}^{2} + a_{h}^{2}} = {{total}\mspace{14mu}{body}\mspace{14mu}{acceleration}\mspace{14mu}{command}}}}{\overset{.}{\psi} = {\frac{a_{h}}{V} = {{turn}\mspace{14mu}{rate}\mspace{14mu}{command}}}}\psi_{i} = {{\psi_{i - 1} + {\overset{.}{\psi}\Delta\; t}} = {{heading}\mspace{14mu}{command}}}}{\overset{.}{\gamma} = {\frac{\left( {a_{v} - g} \right)}{V} = {{flight}\mspace{14mu}{path}\mspace{14mu}{rate}\mspace{14mu}{command}}}}{\gamma_{i} = {{\gamma_{i - 1} + {\overset{.}{\gamma}\Delta\; t}} = {{flight}\mspace{14mu}{path}\mspace{14mu}{angle}\mspace{14mu}{command}}}}{\overset{.}{h} = {{V\;{\sin(\gamma)}} = {{climb}\mspace{14mu}{rate}\mspace{14mu}{command}}}}{h_{i} = {{h_{i = 1} + {\overset{.}{h}\Delta\; t}} = {{altitude}{\mspace{11mu}\;}{command}}}}} & {{Eq}.\mspace{14mu} 57}\end{matrix}$

Additional functionality that can be enabled in a translation layer ismeans for discouraging or preventing an operator (e.g., the human ornon-human operator interfacing the VACS architecture) from overdriving,stalling, or spinning the vehicle frame. This being said, limitingalgorithms can also be employed in the guidance or autopilot functions.

X. Autopilot

As has been addressed, the present invention is not limited to, and doesnot require, a particular autopilot system. The control system andarchitecture embodiments of the present invention can be adapted toaccommodate virtually any autopilot system.

For the purpose of providing an example, an illustrative suitableautopilot software system will now be described. The illustrativeautopilot system incorporates a three-axis design (pitch and yaw with anattitude control loop in the roll axis) for vehicle stabilization andguidance command tracking. The autopilot software design incorporatesflight control techniques, which allow vehicle control algorithms todynamically adjust airframe stabilization parameters in real-time duringflight. The flight computer is programmed directly with the airframephysical properties, so that it can automatically adjust its settingswith changes in airframe configuration, aerodynamic properties, and/orflight state. This provides for a simple and versatile design, andpossesses the critical flexibility needed when adjustments to theairframe configuration become necessary. The three-loop design includesangular rate feedback for stability augmentation, attitude feedback forclosed-loop stiffness, and acceleration feedback for command tracking.In addition, an integral controller in the forward loop illustrativelyprovides enhanced command tracking, low frequency disturbance rejectionand an automatic trim capability.

XI. Multi-Vehicle Ground Control Station

In one aspect of the present invention, an operator station (alsoreferred to as the ground control station or GCS) is designed toaccommodate command and control of multiple vehicles or a single vehicleby a single operator. In accordance with one embodiment, the groundcontrol station is platform independent and implements an applicationprogram interface that provides windowing and communications interfaces(e.g., the platform is implemented in Open Source wxWindows API). Theunderlying operating system is illustratively masked and enables adeveloper to code in a high level environment.

In one embodiment, the ground control station incorporates severalspecialized user interface concepts designed to effectively support asingle operator tasked to control multiple vehicles. The GCS alsoillustratively supports manual control and sensor steering modes. In themanual control mode, the operator can assume control authority of thevehicles individually from the ground control station at any time inflight. In the sensor steering mode, a vehicle will autonomously fly inthe direction the operator is manually pointing the on-board imagingsensor (e.g., operator views video output from a digital camera on a TVinterface, computer screen display, etc.). A custom data link isillustratively utilized to support a two-way transfer of data betweenthe ground control station and the UAV's. These design concepts togetherprovide a flexible, multiple vehicle control system. The details of theconcepts are discussed below.

In one aspect of the present invention, the ground control stationimplemented for flight control includes any or all of the followingcomponents:

-   -   a graphical user interface (GUI)    -   a synthetic vision display    -   two video monitors    -   a laptop computer    -   two repeater displays    -   a hand-held controller    -   a keyboard    -   a mouse control    -   a two-way radio    -   a computer network        The two video monitors are illustratively used to display        real-time data linked camera imagery from two air vehicles        having cameras (of course, fewer, more or none of the vehicles        might have cameras and the number of monitor displays can be        altered accordingly). In accordance with one embodiment, camera        imagery is recorded on videotapes during a mission. In        accordance with one embodiment, the two repeater displays are        used to provide redundant views of the GUI and synthetic vision        display. The laptop illustratively serves as a GUI backup in the        event that the main GUI fails.

FIG. 25 is a simplified block diagram of ground control station 2510 inaccordance with an embodiment of the present invention. As illustrated,ground control station 2510 receives real-time video images through avideo receiver 2512. In accordance with one embodiment, a digital videocamera is installed on one or more of the air vehicles for theproduction of such images. The camera imagery from each camera isillustratively data linked to a dedicated display screen at the groundcontrol station. In accordance with one embodiment, a pan-tilt-zoomcolor camera is illustratively implemented by being installed on theunderside fuselage or the underside of a wing. However, monochromeimagery cameras are also within the scope of the present invention. Inaccordance with one embodiment, cameras are illustrativelyoperator-controlled from the ground control station via a data link tothe vehicle, such as through transceiver 2518.

Video receiver 2512 captures video from a sensor camera and delivers theimaging data to VCR 2514 for video display and processing such thatground control system 2510 can relay processed video through a USB portto notebook computer 2516 for recording onto a hard disk. Notebookcomputer 2516 is configured to playback the recorded video stream.Transceiver 2518 receives data from multiple UAV's as well as transmitsdata to the multiple UAV's. Mode in 2509 supports information transferto and from notebook 2516. Data transmitted to a UAV includes operatorspecific information and non-operator specific information. In addition,a power source 2520 is coupled to notebook computer 2516, video receiver2512, VCR 2514 and a power supply 2522. Power supply 2522 provides powerfor data transmission.

Ground control station 2510 incorporates a graphical user interface thatplaces minimal significance on standard “cockpit” displays and focuseson situational displays. The ground control station display is generallyreconfigurable so that an operator can customize the information layoutto suit his/her specific needs and/or vehicle requirements. An operatorinteracts with the graphical user interface through a mouse, a handheldcontroller (e.g. a joystick, game pad or keyboard arrow keys) akeyboard.

In another aspect of the present invention, an operator is able to exertmanual control of all controlled air vehicles and any associated onboard cameras (e.g., gimbaled cameras) via a hand-held controller, whichis illustratively similar to that utilized in the commercial computergaming industry. In one embodiment, the controller includes twothumb-operated joysticks; one used for steering the selected vehicle,and the other for panning and tilting the camera. In one embodiment, thesystem is configured such that the operator can take manual control ofany vehicle at any time in the mission, and can return to autonomousvehicle control as desired.

In another aspect of the present invention, the mouse control isconfigured to control a cursor on the GUI (e.g., the GUI illustrated inFIG. 26 and described below), for example through standardoperator-initiated “point-and-click” operations, menu options and/oricons. In another embodiment, alphanumeric entries are inserted in theGUI with the keyboard as necessary. In another embodiment, the operatorcan be in voice communication with the flight line personnel throughouta mission with the two-way radio. It should be noted that any othersimilar input and output means (e.g., voice recognition input, etc.) canbe implemented without departing from the scope of the presentinvention.

FIG. 26, in accordance with one aspect of the present invention, is ablock diagram representation of an example GUI display 2622. Inaccordance with one embodiment, display 2622 is subdivided into severalsub-components (e.g., sub-windows). These sub-components illustrativelyinclude a vehicle status display 2624, a vehicle parameter display 2626,a video display 2628, a mission situation display 2629, a verticalprofile display 2631 and a selection pane 2630. In addition, display2622 also includes pop-up dialogs 2630. An operator is able to view moreinformation then that which is displayed in the four sub-components byaccessing various pop-up dialogs 2630. For example, the operator canview details of vehicle parameters, data link parameter details,detailed management of video/IR sensor data and support informationrelated to route editing. It should be noted that this is not anexhaustive list of information sets to which the operator is providedaccess.

In one aspect of the present invention, display 2622 incorporates atleast one intelligent window display having smart variables includedtherein. The concept behind an intelligent window display is that adisplay will function whether or not underlying data is provided througha vehicle data link. The motivation for such a window is to allowdifferent vehicles with different data link variables to use commonwindows for situational awareness. The intelligent window fills thedisplays with ‘smart variables’, allowing the display to be adaptive,and fills in data when it is available. When data is not available, thenthe corresponding data field will appear inactive or grayed out.

FIG. 27 illustrates one illustrative example of a combination vehiclestatus display 2624 and vehicle parameters display 2626. The displayincludes vehicle link parameters 2740 and caution, alerts and warnings(CAWS) pane 2742. Vehicle link parameters pane 2740 illustrativelyincludes critical vehicle parameters such as engine RPM, fuel remainingin accordance with time and distance the vehicle can fly with the fuelremaining, altitude and data link parameters. The CAWS pane 2742illustratively contains active and/or inactive alerts to apprise theoperator of system malfunctions. Examples include: return to baseranges, problems with the programmed route, vehicle performance problemsand various other off-nominal conditions. The CAWS pane 2742 allows anoperator to focus on imagery and mission level tasking with reducedattention to detailed information related to UAV state and health. Withrespect to vehicle status display 2624, the operator can view moredetailed information or pop-up dialogs related to vehicle status bypointing and clicking on various push buttons such as “MORE” button2744.

FIG. 28, in accordance with one aspect of the present invention, is anillustrative screen shot representation of an intelligent window displayin the form of a pop-up dialog 2800 (e.g., as activated by pointing andclicking on the selectable “MORE” button 2744 in FIG. 27). The Route IDbox 2802, the measured altitude box 2804, and the sensor roll angle box2806 are displayed as inactive (i.e., are grayed out) while the rest ofthe display elements are actively updated with data. This isillustratively true because the route ID is not included in thecorresponding vehicle's data link. Similarly, the vehicle isillustratively not equipped with a radar altimeter for ground altitude.Finally, the sensor is illustratively gimbaled in pitch and yaw only, sothe concept of the gimbal roll angle does not make sense for thisconfiguration. The intelligent window accesses the smart variables inthe datalink download list. If the smart variable has not been set, thedisplay simply displays the corresponding control box as inactive.

In accordance with one aspect of the present invention, the describedGUI is configured such that the operator can access one or more controlselection windows configured in a manner similar to the exemplary screenshots provided in FIGS. 29 through 32. FIGS. 29 through 32 togetherrepresent various components of a selections pane 2950 that supports asystem of fully functional dynamic control and management such as can beutilized to manage and control multiple UAV's, as well as correspondingUAV payloads. The GUI is illustratively configured such that theoperator can select and access a selections panel 2950 for any vehicleunder control. As illustrated in FIG. 29, the selections panel 2950includes means for instigating and switching between various levels ofmanual and autonomous control for a corresponding vehicle (withoutdeparting from the scope of the present invention, a fully manualoption, i.e., stick-and-rudder control, could also be presented as a“manual” control mode). When a manual control mode is selected (e.g.,RDC or Sensor Slave), the operator illustratively assumes controlauthority of the corresponding vehicle individually from the groundcontrol station, which can be done at any time in flight. When anautonomous mode is selected, the corresponding autonomous flight controlscheme will be initiated. In some cases, upon selection of an autonomouscontrol mode, the operator is presented with a screen for insertingparameters to which the operator desires the autonomous mode to conform(e.g., the operator can designate a point around which to loiter, etc.).FIG. 33 is one example of a pop-up window designed to collect operatorparameters for a racetrack loiter pattern.

Other selectable features of the selections panel 2950 provide othercontrol options such as auto maneuvers illustrated in FIG. 30, sessionoptions in FIG. 31 and an emergency abort option in FIG. 32 (e.g., fromhere the automated landing process can illustratively be accessed forvehicle recovery). Selections pane 2950 illustratively providesadditional functionality and details such as vehicle parameters, dynamicsensor control capability, a network connectivity ability to broadcastor transmit the UAV video data over LAN or WAN, critical GPS/INSperformance parameters and a TM logging capability in association withthe GCS notebook computer 2516 hard drive (FIG. 25).

With reference to FIG. 26, display 2622 also includes missionsituational display 2629 as well as vertical profile display. Themission situational display 2629 illustratively provides the operatorwith real-time route information for one or more vehicles from a mapperspective. In accordance with one embodiment, display 2629 supportsreal-time route editing. For example, in accordance with one embodiment,a toolbar is displayed across the top of the display and provides anoperator-based rapid, intuitive point and click interaction forreal-time mission planning and route editing capability, as well as mapdisplay editing features (e.g. zoom, center, change map background,etc.). In addition, in accordance with one embodiment, situation display2629 includes a target editor (configured to tie a target to UAV missionobjectives) and a corridor editor (configured to set no-fly zones and/orother mission planning boundary constraints).

The screen shot illustrated in FIG. 33, described in a different contextpreviously, is also one example of a screen shot representation of anintelligent window display in the form of a pop-up dialog for routeediting. The illustrated display provides the operator the capability toeither type in known, precise waypoint coordinates or record graphicallyedited route event coordinates and parameters. This and similar pop-upfunctionality is illustratively provided through display 2622.

A. Synthetic Visualization Tools

In accordance with one aspect of the present invention, a combination ofhigh fidelity synthetic visualization tools, faster than real timesimulation technology, and variable autonomy control together provide abaseline architecture that is capable of supporting an enhanced level ofreal-time UAV control and situation awareness. In accordance with oneembodiment, a synthetically enhanced situation awareness system (SESAS)supports real-time management and control of multiple UAVs by a singleoperator. The synthetic visualization display can include threat datarealistically displayed over mapped and photo-realistic 3D terrain.These visuals are driven (dynamically propagated) by a combination ofsimulated and real UAV data. The simulated data is generated by theground control station and propagated at a higher rate than real data isreceived from the air vehicle. When real data is received, it is used tocorrect the simulation solution, thus providing an accurate, continuousrepresentation of the UAV flight state within its environment.

The described SESAS technology can be utilized to provide a wide fieldof view (FOV) that augments live video and sensor feeds whilecircumventing payload and bandwidth limitations. Specifically,correlated, photo-realistic 3D terrain can be presented on multiplemonitors or flat panel displays to provide a wide area FOV to aidoperators in orientation and situation awareness. Furthermore, inaccordance with one embodiment, the photo-realistic representation ofthe scene can be viewed from various frames of reference (e.g., with thesimple push of a button). For example, one view is an out-the-window(OTW) view that provides a forward-looking wide area view of the scene(this would represent a pilot's cockpit view, for example). Another viewis from above and behind the UAV, providing an outside observer's frameof reference (illustratively including a representation of the vehicle).An additional view is a sensor view in which the live sensor FOV issynthetically increased.

Significant reductions in datalink bandwidth requirements can beachieved with the aid of the simulation. Background and high frequencyupdate information is provided by the simulation, while low-frequencydata specific to the UAV—data that changes in real time over longperiods of time—is provided via downlinks. By filling in the highfrequency gaps with simulated data, very low update rates over thedatalink are made feasible in that the operator is provided with acontinuous situation awareness that is comprised of mixed live andsimulated data. In accordance with one embodiment, a simulated widefield of view from the perspective of an on-board sensor is optionallyprovided (e.g., synthetic data is utilized to expand the sensor view).

The realism afforded by the synthetic visuals significantly enhances theoperator's situation awareness. The synthetic visuals illustrativelyoffer multiple views (or frames of reference) and increasedfield-of-views over that of on-board sensors. In accordance with oneembodiment, video display 2628 in FIG. 26 provides a synthetic visualyet photo-realistic, computer-generated image of the visual environmentof a selected air vehicle (a selected one of several vehicles beingcontrolled by an operator). In accordance with one embodiment, theglobal positioning system (GPS) and inertial navigation system (INS)data that correspond to a vehicle's current position provide an input tothe synthetic visual display, along with the vehicle's flight parameters(e.g., bank angle, pitch angle, heading, and speed). In accordance withone embodiment, special effects, such as target features and explosions,can be programmed in the display. Accordingly, one aspect of the presentinvention pertains to a display system and situation awarenesstechnology that presents the operator with an at least partially virtualrepresentation of the vehicle environment. This enables the operator tobe immersed in the vehicle environment without requiring the expense anddata link bandwidth requirements of extended image based sensor suites.This display technology can be utilized to orient operators of bothmanned and unmanned vehicles. For example, the synthetic display canenable a pilot onboard a vehicle to orient himself relative to actualterrain even when conditions, are dark, cloudy, foggy, etc.

In one embodiment of a synthetic display system in accordance with thepresent invention, a state-of-the-art PC Image Generation (PCIG)component is an incorporated component. Such a component is availablefrom SDS International of Arlington, Va. The PCIG is integrated into thecontrol interface of the present invention to facilitate syntheticallyenhanced operator situation awareness display. The resulting display isa real-time display of 2D and 3D images that can be configured toinclude threats, friendlies, and command control overlays. The visualsoffer complete and current sensor/decision, maker/shooter information,plus situation awareness for safety and navigation.

In one embodiment, synthetic visuals are driven by the vehicle in amanner very similar to a high fidelity flight simulator commandingownship eye-point, environment and other entities. The chief differencebeing that instead of a high fidelity flight simulator, live vehiclestate information drives the ownship eye-point. Furthermore, the otherentities (ground-based threats, other aircraft, etc.) are illustrativelyreal-world sensed entities as opposed to simulated entities.

In one embodiment of the synthetic visual display, the photo-realisticgeo-specific visuals originally developed for training and missionrehearsal are directly utilized in an operational UAV context. In thesimplest terms, the GPS and INS data that report UAV position areutilized as inputs to the Synthetic Visual Display's API, which couplesthe state data with FOV and orientation information from the cameras andsensors onboard the UAV. Replication of the simulated visuals provides“perfect weather”, daylight visuals regardless of the night, weather,fog, clouds, or camera/sensor battle damage. The use of wider Field ofView, multiple screens, augmented symbology and network integrated dataexchange support an entire new generation of situation awarenessenhancements, tools and operator decision aids, especially in thecontext of UAVs with their flexible ground control stations and networkinterconnectivity.

In one aspect of the present invention, synthetic vision displaytechnical approach of the present invention is based upon integratingadvanced simulated visuals, originally developed for training purposes,into UAV operational systems. In accordance with one embodiment, thesimulated visuals are integrated with data derived from the groundcontrol station during flight to enable real-time synthetic visuals.

B. GUI Component Selection

In one aspect of the present invention, through GUI display 2622, anoperator can maintain a variable level of control over a UAV, from fullymanual to fully autonomous, with simple user-friendly inputs. Forexample, if an operator decides to divert a UAV to a new route, theoperator has a plurality of options to select from. The following areexamples of some of the options that an operator has. Those skilled inthe art should recognize that this is not an exhaustive list. In oneembodiment, the operator could graphically edit the existing route onmission situation display 2629 by adding a waypoint or orbit pattern inthe vicinity of a desired target region. Prior to accepting the editedroute, the control system evaluates the revised route against thevehicle performance capability as well as terrain obstructions. If theroute is within acceptable bounds, the control system registers themodified route and maneuvers the vehicle accordingly. In anotherembodiment, the operator could select a park mode on selections pane2630. After selected, the control system queues the operator to clickthe location of and graphical size (via a mouse) the desired orbitpattern in which the vehicle will fly while “parked” over a desiredtarget. In another embodiment, the operator can select a manual controlmode on selections pane 2630. By selecting RDC (remote directionalcommand), for example, the control system controls the UAV into aconstant altitude, heading and speed flight until the operator instructsa maneuver. While in RDC mode, the operator can either pseudo-manuallydirect the UAV using the control stick (e.g. joystick) or the operatorcan program a fixed heading, altitude and speed using the controloptions provided in selections pane 2630.

The described Intelligent displays with smart variables represent aneffective approach to actively displaying information for differenttypes of vehicles. However, a problem can arise when a new vehicle isintegrated into the ground control station with a completely foreigncommand and control interface. Under these circumstances, the groundcontrol station is not concerned about displaying data, but is tasked toprovide a command and control interface for the operator to perform therequired operations. This conundrum is the motivation for anotherembodiment of the present invention, namely, the integration of vehiclespecific panels in the ground control station.

In one embodiment, a generic vehicle class (GVC) is illustratively asoftware component that provides a rapid development environment API toadd new vehicle classes and types to the ground control station. The GVCalso illustratively serves as a software construct that allows theinclusion of multiple vehicles within the ground control stationframework. One of the variables in the application is a vector ofpointers to a generic vehicle class. This list is constructed byallocating new specific vehicles and returning a type case to the basegeneric vehicle class. When a new vehicle is integrated into the groundcontrol station, the generic vehicle class provides all of the virtualfunctions to integrate with system control components (e.g., tointegrate with a map display, a communications package, PCIG imageryand/or appropriate display windows). An important object in theapplication framework is illustratively a pointer to the current vehiclegeneric class. When the user switches vehicles, this pointer is updatedand all displays grab the appropriate smart variables from the pointerto the new base class. This is the mechanism by which windowsimmediately update to the current vehicle information whenever the userswitches vehicles. The default windows use the pointer to the currentvehicle to grab information. In this manner, if the user switches to anew vehicle with a different set of datalink variables, that fact isimmediately apparent on the display windows.

FIG. 34 is a schematic block diagram demonstrating implementation ofvehicle specific panels. Through base control station 3402, an operatorhas access to a plurality of vehicle classes labeled as 3404, 3414 and3424 (others can be included as well). Each vehicle class illustrativelycontains a pointer to associated vehicle specific windows, along withvirtual functions that can be asserted to provide an appropriatedisplay. When a vehicle is selected, the appropriate vehicle specificinformation (i.e., windows 3406, 3408, 3410, 3412, etc.) will bedisplayed.

In one embodiment, a given vehicle can be configured to select defaultpanels, in which case vehicle specific panels will not be provided forthat particular vehicle class. In one embodiment, if a default windowdoes not provide a particular functionality required by a new vehicle, anew vehicle specific class can override those base windows and the newwindows will be displayed upon selection.

FIGS. 35 and 36 are screen shot representations demonstrating vehiclespecific sensor control windows. FIG. 35 is illustratively a vehiclespecific control window for a vehicle identified as Dakota1. FIG. 36 isillustratively a vehicle specific control window for a vehicleidentified as Dakota2. Whenever Dakota1 is selected as the activevehicle, the platform includes a steerable sensor with an optional IRdigital camera. However, the Dakota2 variant has no steerable camera atall. Instead, it is equipped with a fixed camera and a Ground CollisionAvoidance System. When the user selects Dakota2 as the active vehicle,the sensor control window switches to the vehicle specific sensorwindow. This window allows the user the option to turn on and off theground collision avoidance system.

The described ability to tailor the ground control station windowsenables any vehicle to be integrated with the ground control stationwithout loss of information from the previously integrated vehicles.Accordingly, the ground control station supports a multi heterogeneousplatform command and control application. One potential limitation onthe number of selectable vehicles is the throughput of the collectivedatalink packages.

Referring back to mission situation display 2629 of FIG. 26, eachvehicle is illustratively represented on the display (e.g., the mapdisplay) by a symbol (e.g., a representation of a vehicle). A vehiclesymbol moves across the display, typically an illustrated map, inaccordance with movement of the actual vehicle (e.g., movement relativeto the map is to scale). The path of where a vehicle has been (and/orwhere the vehicle has been directed to go) is illustratively representedby a line. In one embodiment, each vehicle and its associated path linesare displayed in a unique color so as to distinguish one vehicle'sactivity from another. The interface is illustratively configured suchthat a user can click directly on the display and thereby select one ofthe vehicles causing vehicle specific control windows to be displayedfor the selected vehicle. Once a vehicle is selected, the system isconfigured such that the user can change the mode of control for theselected vehicle. In the context of the VACS design described herein,the operator can select from the range of available variable autonomouscontrol modes. In accordance with one embodiment, if the operatorswitches control to a second vehicle without leaving adequateprospective flight instructions for the first vehicle, then the firstvehicle will “hold steady” (e.g., steady velocity, altitude, etc.) untildirect control is resumed.

FIG. 37 is a screen shot representation of a detailed operator controlgraphical user interface display in accordance with an embodiment of thepresent invention. The display includes a mission situation display 3702illustratively configured in a manner similar to the map displaydescribed in the preceding paragraph. Window 3704 is illustrativelyconfigured for operating data and function display. FIG. 37 isillustratively configured to display data and functions related to GPSand/or camera functionality. Window 3708 is illustratively a windowconfigured to display data and functionality related to various systemparameters. Window 3710 is illustratively configured to display data andfunctionality related to the navigation system. Finally, window 3712 isconfigured to display data and functionality related to control modes(e.g., operator can interact with this window to change control modesfor a given vehicle). Displayed windows are illustratively configuredfor relocation and reconfiguration as desired by a particular operator.In one embodiment, the vehicle for which displayed parameters areassociated depends on which vehicle has been selected by the operator.Again, the map display can illustratively be configured to show allvehicles relative to one another (and relative to the map) regardless ofwhich vehicle is selected.

In one aspect of the present invention, the dynamic information in thedialog windows and navigation map is updated as the flight progressesand as the flight parameters undergo change. The vehicle informationthat is displayed corresponds to the vehicle the operator selects(simply clicking on the appropriate vehicle icon in the map display),and any one of the vehicles currently in flight can be selected. The mapdisplay provides a photographic depiction of the mission site, therelative locations of the air vehicles at the site, and the plannedroutes of the vehicles. An image output synthetic or otherwise, canalternatively be portrayed on the map display (alternatively, sensordata and/or synthetic image data can be displayed on separate monitors).The vehicle icons and the navigation routes are illustrativelycolor-coded and highlighted on the map display as the vehicles areindividually selected. Route planning can be performed from the mapdisplay, and route editing (e.g., changing waypoint locations) can beaccomplished at any time in a mission. The map display also provides adepiction of the imaging payload field of view and the terrain areaencompassed within it. The location and types of targets in the flightenvironment can also be represented on the may display. A profile viewshowing the height of the operator-selected vehicle above to the terraincan be displayed below the map. Various drop-down menus are alsoavailable to the operator from the GUI.

In one embodiment, for vehicles that incorporate a visual sensor (e.g.,a digital camera), the vehicle indicated on the map display includes asensor window indication displayed proximate to the vehicle indication(e.g., a box located in front of the vehicle indication). The dimensionsof the sensor window indication illustratively corresponds to a field ofview for the camera as it is displayed on a monitor in a controlstation. If the operator guides the vehicle or camera so as to open up abroader field of view, then the box indication illustratively becomeslarger. Conversely, if the operator guides the vehicle or camera so asto narrow the field of view, then the box indication illustrativelybecomes smaller.

In review, a VACS human-system interface (HSI) is implemented with agraphical user interface (GUI) that allows the operator to quickly alterthe UAV course with little effort. The VACS HSI focuses on the UAVmission tasking rather than vehicle aviation; hence, the VACS interfaceplaces minimal significance on standard “cockpit” displays and focuseson situation displays. The operator interacts with VACS through the useof a mouse, a joystick (or game pad), and/or a keyboard. The softwarecan easily be modified to take advantage of touch-screen capabilities aswell.

In accordance with one embodiment, a ground control station display isdivided into 4 subcomponents: a vehicle status display, a situationdisplay, a video display, and a selection pane. This interface containsa route editing dialog to support real-time route editing as well as avariety of selection panes to support fully functional dynamic controland management of the UAV.

In accordance with one embodiment, push buttons in the main GUI provideaccess to additional dialogs that provide vehicle status information,sensor management and control functionality, and informationdissemination capability through both data logging and networkconnectivity. A route editing dialog is accessed from the map displayand provides the operator rapid, intuitive point-n-click systeminteraction for real-time mission planning and route editing capability,as well as map display editing features (zoom, center, change mapbackground, etc). The route editing pop-up dialog provides the operatorthe capability to either type in known, precise waypoint coordinates orrecord graphically edited route event coordinates and parameters. Thesituation (map) display also contains a target editor with thecapability to tie targets to UAV mission objectives and a corridoreditor set no-fly zones and/or other mission planning boundaryconstraints.

In accordance with one embodiment, mission/route editing is performedmanually by the operator, using the graphical user interface“point-n-click” functionality on the map or typing in the coordinates.The interface, however, is illustratively designed generically soautomated route plans can be accepted. VACS contains automaticroute/mission analysis tools to alert the operator if a planned missionis not physically realizable due to vehicle performance constraints orterrain collision issues.

In accordance with one embodiment, the VACS GCS also contains aCautions, Alerts, and Warnings (CAWS) panel that alerts the operator tosystem malfunctions, low fuel, route errors, and various otheroff-nominal conditions. The CAWS display will alert the operator when avehicle subsystem fault is detected.

Using the VACS GUI interface, the operator can maintain any level ofcontrol over the UAV, from fully manual to fully autonomous, with thesimple click of a mouse. For example, if the UAV is flying apreprogrammed waypoint route and the operator decides to divert it fromthat route to a new desired location, he/she has a myriad of options athis disposal. For example, a few of the options are:

-   1. Graphically edit the existing route on the mission situation    display by adding a waypoint or orbit pattern in the vicinity of the    desired target region. Prior to accepting the edited route, VACS    evaluates the revised route against the vehicle performance    capability as well as terrain obstructions. If the route is within    acceptable performance bounds, VACS then registers the modified    route into the outer-loop control function and the vehicle maneuvers    accordingly.-   2. Select “Go To” point on the 2D situation map display. When this    mode is selected, VACS will queue the operator to click the location    of and graphically size (via the mouse) the desired orbit pattern,    which the vehicle is to fly while “parked” over a target area.-   3. Select a manual control mode on the vehicle selections panel. By    selecting RDR (remote directional response), for example, VACS    controls the UAV into a constant altitude, constant heading, and    constant speed flight condition until the operator instructs a    maneuver. While in RDR mode, the operator can either:    -   a. Pseudo-manually direct the UAV using the control stick        (horizontal stick commands map to horizontal turn rates,        vertical stick commands map to vertical climb/descent rates).    -   b. Program in a fixed heading, altitude, and speed using the        control options provided in the route tab of the selection pane.        XII. Datalink

In one aspect of the present invention, in order to facilitatesimplified multi-vehicle communications, the ground control stationimplements a UDP/IP (user datagram protocol/internet protocol) standard.This configuration enables the underlying operating system to organizeand multiplex data based on IP addresses. In one embodiment, the genericvehicle class system provides a means for assigning a vehicle IPaddress. When all system IP addresses are known, each vehicle providesits data link messages and the ground control station forwards thosemessages to the appropriate Internet address. In one embodiment, thistype of data collection is used primarily for uplink information.

One aspect of the present invention pertains to the parsing of downlinkmessages. One embodiment pertains to an implementation of the knownserial line Internet protocol (SLIP). The SLIP protocol takes standardIP type information and encodes it to a serial stream to be sent over aserial device. On the other side, a decoder converts the serial streamback to IP so the computers on each side of the interface do not knowabout the underlying serial protocol—to them, communication isconsistent with IP over Ethernet links.

In accordance with one embodiment of the present invention, the groundcontrol station actually connects to a router (e.g., a SLIP router),which takes all of the information from the ground control station andforwards it to the appropriate vehicle. In accordance with oneembodiment, this enables a user of hybrid hardware systems with 802.11bamplified cards or serial communication radios (e.g., Freewave radios)which run the SLIP protocol to mask the underlying serial interface.With this setup, the ground control station always connects to vehiclesas if they were computers on a network, and all routing is taken care ofby the router. Thus, data packets going over serial communication radiointerfaces (e.g., Freewave radio interfaces) are run through the SLIPprotocol and data packages going over 802.11b amplified cards areforwarded without processing. It should be noted that a SLIP router andSLIP protocol are provided as examples of a suitable implementation.Other similar known communications implementations could be incorporatedwithout departing from the scope of the present invention.

The reading of download data links becomes a bit complex. The reason isthat the ground control station always talks to the SLIP box, soinformation from any vehicle is effectively coming from the sameInternet address. Therefore, in accordance with one embodiment, theground control station monitors a specific designated port for allincoming data. The data has an assumed header that contains a vehicle IDand message size. The communications package then forwards the datalinkinformation to the appropriate vehicle class.

FIG. 38 is a schematic block diagram demonstrating a network centric UDPcommunications scheme in accordance with one embodiment of the presentinvention. Vehicles 3804, 3806, 3808 and 3810 each include anillustrated IP address and communicate with ground control station 3812by way of router (e.g., SLIP protocol means) 3802. Station 3812 alsoincludes an illustrated IP address. It should be noted that othercomponents can be assigned IP addresses and added to the communicationsloop. For example, within FIG. 38, a visual system 3814 is illustratedand includes an illustrated IP address for communications support.

Accordingly, one aspect of the present invention pertains to aspread-spectrum communications hardware architecture and supportingmulti-layered communications software packages that enable multi-vehicleIP-based messaging (TCP, UDP). This IP-based messaging design enablesmulti-vehicle control using either conventional radios driven by serialinterfaces or wireless Ethernet boards (i.e., 802.11).

One advantage of the described multi-vehicle communications architectureis compatibility with conventional spread-spectrum data link systemsthat operate with standard serial interfaces. An Ethernet-to-transceiverbridge provides a transparent IP (TCP or UDP) network interface for theGround Control Station (GCS) to interface to multiple UAVs. Inaccordance with one embodiment, to utilize wireless Ethernet (i.e.,802.11) technology, the bridge and spread-spectrum radios are simplyreplaced with the 802.11 board—no software modifications are required.

XIII. Flight Control System Hardware

In accordance with one aspect of the present invention, the VACSarchitecture is applied in the context of an integrated UAV digitalflight control system and ground control system. In accordance with oneembodiment, the airborne digital flight control system is implemented inthe context of a computing environment (e.g., a PC/104 stack) configuredfor guidance, navigation, and control processing, power distribution,I/O handling, and/or a data link system. Depending on a givenapplication and implementation, the computing environment can also beconfigured to support an inertial measurement unit (IMU), a precisionpressure transducer for airspeed measurements, a GPS receiver, and/or acontrol interface to a pan-tilt-zoom or gimbaled payload system. Aninterface controller box can also be provided to allow the UAV to beoperated by either the VACS controller or a back-up radio control (R/C)transmitter. As has been described, the airborne system guidance andautopilot software is capable of supporting varying levels of controlautonomy.

XIV. Sample Mission

The described VACS architecture and user interface control systemenables an example mission as follows. In the example scenario, threeUAV's are simultaneously controlled by a single operator from a groundcontrol station. The operator controls the vehicles during a simulatedtarget search and destroy mission. Two of the vehicles image a ground“target”, using on-board digital cameras, and one of the vehiclesperforms a simulated target attack maneuver. Each vehicle providesvarious autonomous flight control capabilities to the operator,including autonomous waypoint navigation, various orbit patterns fortime-on-target, loss-of-link and return-to-base (automatic landinginitiated to preprogrammed or operator-designated location whencommunications link lost), and automatic ground collision avoidance.

In accordance with the example mission, three air vehicles are flownsimultaneously, simulating a target search and destroy mission. Thevehicles are launched individually under the control of an RIC pilot,who is located near the takeoff point on an airfield runway. The pilotremotely steers each of the vehicles to a transition point, wherevehicle control is switched over to the GCS operator. Following theswitchover, the operator manually steers the vehicle toward apre-planned orbit pattern. After the vehicle is properly oriented, theoperator commands the VACS control system and the vehicle fliesautonomously to the orbit pattern. The vehicles all orbit at an altitudeof 1500-ft. MSL (˜1000-ft. AGL) and at a speed of approximately 75 kts.

One of the vehicles illustratively circles near the end of the runwayand briefly images the runway as it circles. An automobile, representinga ground target, is positioned on the runway. The air vehicle is thencommanded to a lower altitude in the orbit pattern to simulate a targetsurveillance maneuver. The vehicle is then commanded to climb to itsoriginal orbiting altitude.

Next, the operator redirects one of the vehicles and sends it from itsorbit pattern to the runway by designating a target location on thesituation display and invoking a “go to” mode. The UAV autonomouslycaptures and enters an orbit patter over the target and automaticallysteers the camera to maintain persistent surveillance of the target.Subsequently, the vehicle autonomously returns to the orbit pattern.

The operator then decouples the VACS automation on another vehicle andprograms a new route to pass over the runway. Near the runway thevehicle is sent to a lower altitude to simulate a weapon attack. Afterseveral passes over the runway, the vehicle is returned to its initialaltitude and the vehicle autonomously returns to its pre-assigned orbitpattern.

Vehicle speeds are always maintained at about 75 kts. The autonomouslanding system of the present invention is engaged to return thevehicles to the runway from which they took off. An automated take-offcan illustratively also be implemented to eliminate the necessity of anRC controller for landing/take-off.

FIG. 39 is a schematic block diagram illustrating potential controlpaths through a mission in accordance with the VACS architecture. Block3902 represents the potential missions that can be executed such assurveillance, reconnaissance and/or target acquisition. Of course, othermissions, including non-military related missions, are within the scopeof the present invention. Block 3904 represents the step of planning amission. Block 3906 represents launching a vehicle. Block 3908represents monitoring system status after launch. Block 3910 representsevaluating whether a critical system failure has occurred. If such afailure does occur, then the mission is aborted in accordance with block3912 (e.g., the vehicle is recovered in accordance with an automatedlanding process execution). Such monitoring is executed in a loop tocontinually watch for critical failures.

In accordance with block 3914, reconnaissance data is gathered ifnecessary. Block 3916 represents vehicle mission management. Inaccordance with block 3918, communication links are monitored. If acommunication link is interrupted, then link loss procedures areimplemented in accordance with block 3920 (e.g., automatic landingsystem is initiated for vehicle recovery). In accordance with block3922, the operator manages the route the vehicle is set to follow. Inaccordance with block 3928, the operator can edit the route. If anon-valid route is entered, then the route must be edited again.Otherwise, the valid route is executed. This is but one means of controlavailable to the operator for mission execution.

In accordance with block 3926, the operator manages sensors associatedwith the vehicle. Block 3934 indicates selection of a sensor. Inaccordance with block 3936, a sensor control mode can be set. One of thesensor control mode settings available corresponds to block 3944 and isan auto-tracking functionality wherein the sensor will automaticallytrack as necessary. Block 3946 represents a manual control of the sensorand block 3948 represents steering of the sensor. Block 3950 representssensor control based on a designated target.

Block 3924 represents control mode management by the operator. Inaccordance with block 3930, the operator can choose an autonomouscontrol mode such as, but not limited to, vehicle route management. Inaccordance with block 3932, the operator can select a manual controlmode. In accordance with block 3938, the operator can choose RDRcontrol. In accordance with block 3952, the vehicle can be steered inthe horizontal and vertical planes. These modes can be executed asnecessary to support achievement of mission objectives in accordancewith block 3962.

Another available mode of control is line-of-sight-slave control inaccordance with block 3940. In accordance with block 3954 the vehiclesensor is utilized for steering purposes as necessary to supportachievement of mission objectives. Block 3942 represents programmaneuver control. Block 3956, 3960 and 3958 represent a setting ofparameters for programmed maneuver control. The program maneuver controlcan also be selected to support the achievement of mission objectives.In accordance with block 3962, analysis is conducted to determinewhether mission objectives have been achieved. If they have not, thenthe control processes are continued. If the objectives have beenachieved, then, in accordance with block 3964 and 3966, the vehicle isrecovered (e.g., automated landing system is implemented if necessary).In accordance with one embodiment, radio control is utilized to launchand/or recover a vehicle.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

1. A method of landing an unmanned aerial vehicle comprising:programming a landing location for the unmanned aerial vehicle utilizinga user input device; launching the unmanned aerial vehicle; interruptingcommunications between with the unmanned aerial vehicle and the userinput device; and landing the unmanned aerial vehicle at the landinglocation based on the programmed landing location and not based on anyreal-time communication between the unmanned aerial vehicle and the userinput device.
 2. The method of claim 1, wherein programming the landinglocation is performed before launching the unmanned aerial vehicle. 3.The method of claim 1, wherein programming the landing location isperformed after launching the unmanned aerial vehicle.
 4. The method ofclaim 1, wherein the landing location is an airfield runway.
 5. Themethod of claim 1, wherein the landing location is not an airfieldrunway.
 6. The method of claim 1, wherein the landing location is a samelocation as a launching location.
 7. The method of claim 1, wherein thelanding location is a different location than a launching location. 8.The method of claim 1, wherein programming comprises receiving anoperator path input.
 9. An unmanned aerial vehicle control systemcomprising: a guidance unit that receives flight commands from aplurality of subunits, the subunits having varying levels of autonomy,one of the subunits including a preprogrammed maneuvers subunit, thepreprogrammed maneuvers subunit providing landing information includinga landing location for the unmanned aerial vehicle; a translation unitthat receives guidance information from the guidance unit and convertsthe guidance information into acceleration vectors; and an autopilotunit that controls operations of the unmanned aerial vehicle, theautopilot unit receiving the acceleration vectors from the translationunit and landing the unmanned aerial vehicle at the landing locationbased on the acceleration vectors.
 10. The system of claim 9, whereinthe landing location is one of a plurality of preprogrammed locations.11. The system of claim 9, wherein the landing location is anoperator-designated location.
 12. The system of claim 9, wherein thelanding location for the unmanned aerial vehicle is entered before theunmanned aerial vehicle takes-off.
 13. The system of claim 9, whereinthe landing location for the unmanned aerial vehicle is entered duringflight.
 14. The system of claim 9, wherein the landing location is asame location as a take-off location.
 15. The system of claim 9, whereinthe landing location is a different location than a take-off location.16. An unmanned aerial vehicle control system comprising: a groundcontrol station having a user interface, the user interface receiving anindication of a landing location; a data link for transferringinformation between the ground control station and the unmanned aerialvehicle; and a variable autonomy flight guidance system onboard theunmanned aerial vehicle that lands the unmanned aerial vehicle at thelanding location based on receiving the indication from the data link.17. The system of claim 16, wherein the variable autonomy flightguidance system controls descent operations of the unmanned aerialvehicle.
 18. The system of claim 16, wherein the variable autonomyflight guidance system controls flare operations of the unmanned aerialvehicle.
 19. The system of claim 16, wherein the variable autonomyflight guidance system controls lateral motion operations of theunmanned aerial vehicle.
 20. The system of claim 16, wherein thevariable autonomy flight guidance system controls ground roll operationsof the unmanned aerial vehicle.
 21. The system of claim 16, wherein thevariable autonomy flight guidance system controls taxi operations of theunmanned aerial vehicle.